Energy companies cannot be charged a fully commercial price by the government for disposing of nuclear waste without “killing the prospect” of a new generation of reactors, a government adviser will warn on Thursday.

The analysis will fuel opposition to the government’s contentious and aggressive drive to expand the UK’s nuclear capacity. Gordon Brown will on Thursday underscore his determination to attract investors to build reactors, at his summit with Nicolas Sarkozy, the French president. The leaders are expected to agree to Anglo-French co-operation on nuclear skills and regulation.