The Third International after Lenin by Leon Trotsky (1928) can be purchased here.
The below excerpt is from the section "7. On the Reactionary Idea of "Two-Class Workers' and Peasants' Parties" for the Orient."
….The Opposition, as is known, insisted on the withdrawal of the party from the Kuomintang:
"The question arises," says Bukharin, "why? Is it because the leaders of the Kuomintang are vacillating? And what about the Kuomintang masses, are they mere 'cattle'? Since when is the attitude to a mass organization determined by what takes place at the 'high' summit!" 
The very possibility of such an argument seems impossible in a Revolutionary party. Bukharin asks, "And what about the Kuomintang masses, are they mere cattle?" Of course they are cattle. The masses of any bourgeois party are always cattle, although in different degrees. But for us, the masses are not cattle, are they? No, that is precisely why we are forbidden to drive them into the arms of the bourgeoisie, camouflaging the latter under the label of a workers' and peasants' party. That is precisely why we are forbidden to subordinate the proletarian party to a bourgeois party, but on the contrary, must at every step, oppose the former to the latter. The "high" summit of the Kuomintang of whom Bukharin speaks so ironically, as of something secondary, accidental, and temporary is in reality the soul of the Kuomintang, its social essence. Of course, the bourgeoisie constitutes only the "summit" in the party as well as in society. But this summit is powerful in its capital, knowledge, and connections: it can always fall back on the imperialists for support, and what is most important, it can always resort to the actual political and military power which is intimately fused with the leadership in the Kuomintang itself. It is precisely this summit that wrote laws against strikes, throttled the uprisings of the peasants, shoved the communists into a dark corner, and, at best, allowed them to be only one-third of the party, exacted an oath from them that petty-bourgeois Sun Yat-senism takes precedence over Marxism. The rank and file were picked and harnessed by this summit, serving it, like Moscow, as a "Left" support, just as the generals, compradores, and imperialists served it as a Right support. To consider the Kuomintang not as a bourgeois party, but as a neutral arena of struggle for the masses, to play with words about nine-tenths of the Left rank and file in order to mask the question as to who is the real master, meant to add to the strength and power of the summit, to assist the latter to convert ever broader masses into "cattle," and, under conditions most favorable to it to prepare the Shanghai coup d'etat. Basing themselves on the reactionary idea of the two-class party, Stalin and Bukharin imagined that the communists, together with the "Lefts," would secure a majority in the Kuomintang and thereby power in the country, for, in China, power is in the hands of the Kuomintang. In other words, they imagined that by means of ordinary elections at Kuomintang Congresses power would pass from the hands of the bourgeoisie to the proletariat. Can one conceive of a more touching and idealistic idolization of "party democracy" ... in a bourgeois part? For indeed, the army, the bureaucracy, the press, the capital are all in the hands of the bourgeoisie. Precisely because of this and this alone it stands at the helm of the ruling party. The bourgeois "summit" tolerates or tolerated "nine-tenths" of the Lefts (and Lefts of this sort), only in so far as they did not venture against the army, the bureaucracy, the press, and against capital. By these powerful means the bourgeois summit kept in subjection not only the so-called nine-tenths of the "Left" party members, but also the masses as a whole. In this the theory of the bloc of classes, the theory that the Kuomintang is a workers' and peasants' party, provides the best possible assistance for the bourgeoisie. When the bourgeoisie later comes into hostile conflict with the masses and shoots them down, in this clash between the two real forces, the bourgeoisie and the proletariat, not even the bleating of the celebrated nine-tenths is heard. The pitiful democratic fiction evaporates without a trace in face of the bloody reality of the class struggle.
Such is the genuine and only possible political mechanism of the "two-class workers' and peasants' parties for the Orient." There is no other and there will be none.
Although the idea of the two-class parties is motivated on national oppression, which allegedly abrogates Marx's class doctrine, we have already heard about "workers' and peasants' " mongrels in Japan, where there is no national oppression at all. But that isn't all, the matter is not limited merely to the Orient. The "two-class" idea seeks to attain universality. In this domain, the most grotesque features were assumed by the above-mentioned Communist Party of America in its effort to support the presidential candidacy of the bourgeois, "anti-trust" Senator LaFollette, so as to yoke the American farmers by this means to the chariot of the social revolution. Pepper [József Pogány], the theoretician of this maneuver, one of those who ruined the Hungarian revolution because he overlooked the Hungarian peasantry, made a great effort (by way of compensation, no doubt) to ruin the Communist Party of America by dissolving it among the farmers. Pepper's theory was that the super-profit of American capitalism converts the American proletariat into a world labor aristocracy, while the agrarian crisis ruins the farmers and drives them onto the path of social revolution. According to Pepper's conception, a party of a few thousand members, consisting chiefly of immigrants, had to fuse with the farmers through the medium of a bourgeois party and by thus founding a "two-class" party, insure the socialist revolution in the face of the passivity or neutrality of the proletariat corrupted by super-profits. This insane idea found supporters and half-supporters among the upper leadership of the Comintern. For several weeks the issue swayed in the balance until finally a concession was made to the ABC of Marxism (the comment behind the scenes was: Trotskyist prejudices). It was necessary to lasso the American Communist Party in order to tear it away from the LaFollette party which died even before its founder.
Everything invented by modern revisionism for the Orient is carried over later to the West. If Pepper on one side of the Atlantic Ocean tried to spur history by means of a two-class party then the latest dispatches in the press inform us that the Kuomintang experience finds its imitators in Italy where, apparently, an attempt is being made to foist on our party the monstrous slogan of a "republican assembly on the basis [?!] of workers' and peasants' committees." In this slogan the spirit of Chiang Kai-shek embraces the spirit of Hilferding. Will we really come to that?
In conclusion there remains for us only to recall that the idea of a workers' and peasants' party sweeps from the history of Bolshevism the entire struggle against the Populists (Narodniks), without which there would have been no Bolshevik party. What was the significance of this historical struggle? In 1909, Lenin wrote the following about the Social-Revolutionists:
"The fundamental idea of their program was not at all that 'an alliance of the forces' of the proletariat and the peasantry is necessary, but that there is no class abyss between the former and the latter and that there is no need to draw a line of class demarcation beween them, and that the social democratic idea of the petty bourgeois nature of the peasantry that distinguishes it from the proletariat is fundamentally false." 
In other words, the two-class workers' and peasants' party is the central idea of the Russian Narodniks. Only in the struggle against this idea could the party of the proletarian vanguard in peasant Russia develop.
Lenin persistently and untiringly repeated in the epoch of the 1905 revolution that
"Our attitude towards the peasantry must be distrustful, we must organize separately from it, be ready for a struggle against it, to the extent that the peasantry comes forward as a reactionary or anti-proletarian force." 
In 1906 Lenin wrote:
"Our last advice: proletarians and semi-proletarians of city and country, organize yourselves separately! Place no trust in any small proprietors, even the petty ones, even those who 'toil' … We support the peasant movement to the end, but we must remember that it is a movement of another class, not the one that can or will accomplish the socialist revolution." 
This idea reappears in hundreds of Lenin's major and minor works. In 1908, he explained:
"The alliance between the proletariat and the peasantry must in no case be interpreted to mean a fusion of the different classes or parties of the proletariat and the peasantry. Not only fusion, but even any sort of lasting concord would be fatal for the socialist party of the working class and weaken the revolutionary democratic struggle." 
Could one condemn the very idea of a workers' and peasants' party more harshly, more ruthlessly, and more devastatingly?
Stalin, on the other hand, teaches that
"The revolutionary anti-imperialist bloc … must, though not always [!] necessarily [!], assume the form of a single workers' and peasants' party, bound formally [?] by a single platform." 
Lenin taught us that an alliance between workers and peasants must in no case and never lead to merger of the parties. But Stalin makes only one concession to Lenin: although, according to Stalin, the bloc of classes must assume "the form of a single party," a workers' and peasants' party like the Kuomintang – is not always obligatory. We should thank him for at least this concession.
Lenin put this question in the same irreconcilable spirit during the epoch of the October Revolution. In generalizing the experience of the three Russian revolutions, Lenin, beginning with 1918, did not miss a single opportunity to repeat that there are two decisive forces in a society where capitalist relations predominate'the bourgeoisie and the proletariat.
"If the peasant does not follow the workers, he marches behind the bourgeoisie. There is and there can be no middle course." 
Yet a "workers" and peasants' party" is precisely an attempt to create a middle course.
Had the vanguard of the Russian proletariat failed to oppose itself to the peasantry, had it failed to wage a ruthless struggle against the all-devouring petty-bourgeois amorphousness of the latter, it would inevitably have dissolved itself among the petty-bourgeois elements through the medium of the Social Revolutionary Party or some other "two-class party" which, in turn, would inevitably have subjected the vanguard to bourgeois leadership. In order to arrive at a revolutionary alliance with the peasantry – this does not come gratuitously – it is first of all necessary to separate the proletarian vanguard, and thereby the working class as a whole, from the petty bourgeois masses. This can be achieved only by training the proletarian party in the spirit of unshakable class irreconcilability.
The younger the proletariat, the fresher and more direct its "blood-ties" with the peasantry, the greater the proportion of the peasantry to the population as a whole, the greater becomes the importance of the struggle against any form of "two-class" political alchemy. In the West the idea of a workers' and peasants' party is simply ridiculous. In the East it is fatal. In China, India, and Japan this idea is mortally hostile not only to the hegemony of the proletariat in the revolution but also to the most elementary independence of the proletarian vanguard. The workers' and peasants' party can only serve as a base, a screen, and a springboard for the bourgeoisie.
It is fatal that in this question, fundamental for the entire East, modern revisionism only repeats the errors of old social democratic opportunism of pre-revolutionary days. Most of the leaders of European social democracy considered the struggle of our party against SRs to be mistaken and insistently advocated the fusion of the two parties, holding that for the Russian "East" a two-class workers' and peasants' party was exactly in order. Had we heeded their counsel, we should never have achieved either the alliance of the workers and the peasants or the dictatorship of the proletariat. The "two-class" workers' and peasants' party of the SRs became, and could not help becoming in our country, the agency of the imperialist bourgeoisie, i.e., it tried unsuccessfully to fulfill the same historic role which was successfully played in China by the Kuomintang in a different and "peculiar" Chinese way, thanks to the revisionists of Bolshevism. Without a relentless condemnation of the very idea of workers' and peasants' parties for the East, there is not and there cannot be a program of the Comintern.