Through his labour theory he tries to explain the cause of the class structure in a capitalist system, like surplus value, low wages etc. I want to say that both the theories are parts of one chain of the Marx's theory of communism. Consult Judd Harmon's "Political Thought: From Plato to Present". Good luck!

__________________
"Success is not final, failure is not fatal; it is the courage to continue that counts" (Winston Churchill)