By the example of the English-language political texts the author considers false propositions in insincere discourse. The purpose of the paper is to study the features of the functioning of these propositions in the specified type of texts. The topicality of the work is conditioned by the interest in linguistics to texts (discourse) of a different linguistic nature, including the insincere one. The author comes to the conclusion that insincerity as a linguistic phenomenon is a strategy realized with the help of certain tactics, and the violation of propositions in the linguistic material under consideration consists in attributing false features and false actions to objects.