The Prime Minister, Gordon Brown, faced a sharp rebuff over Europe after a Labour-dominated committee attacked the "secrecy" of European reform.

The Commons European Scrutiny Committee also contradicted the repeated statements of ministers that the proposed EU reform treaty significantly differed from the planned EU constitution, which was abandoned after it was rejected by French and Dutch voters.

A report by the committee said: "Taken as a whole, the reform treaty produces a general framework which is substantially equivalent to the constitutional treaty." It also warned that Britain may not be able to maintain its "red lines" over important policy areas.

The report, published just days before European leaders meet in Lisbon to thrash out a final deal on the reforms, gives ammunition to sceptics who say the treaty should go to a referendum.