The present invention relates to a proton-conducting polymer membrane which comprises polyazole blends and is obtainable by a process comprising the steps A) preparation of a mixture comprising polyphosphoric acid, at least one polyazole (polymer A) and/or one or more compounds which are suitable for forming polyazoles under the action of heat according to step B), B) heating of the mixture obtainable according to step A) under inert gas to temperatures of up to 400.degree. C., C) application of a layer using the mixture from step A) and/or B) to a support, D) treatment of the membrane formed in step C) until it is self-supporting, wherein at least one further polymer (polymer B) which is not a polyazole is added to the composition obtainable according to step A) and/or step B) and the weight ratio of polyazole to polymer B is in the range from 0.1 to 50.