Two Norfolk Tory MPs are contributing to growing pressure on David Cameron to promise a referendum on the EU reform treaty even if it is ratified before their party regains power.

By Chris Fisher, Political editor

Two Norfolk Tory MPs are contributing to growing pressure on David Cameron to promise a referendum on the EU reform treaty even if it is ratified before their party regains power.

Almost a quarter of Conservative MPs are now backing a referendum “before or after ratification” and they include Richard Bacon (South Norfolk) and Christopher Fraser (SW Norfolk).

Mr Cameron has led demands for prime minister Gordon Brown to hold a referendum on the treaty, arguing it is virtually identical to the EU constitution rejected by French and Dutch voters two years ago. But he has doggedly refused to commit himself to holding a referendum on the subject on becoming prime minister if by then the treaty has already been ratified.

In response to such calls he has emphasised that “the time for a referendum is now”. But over 40 of the Conservative Party's 197 MPs have backed a Commons motion calling for a referendum regardless of ratification.

Mr Cameron is believed to have taken the line he has partly because of the complexities involved in pulling out of an already ratified treaty and partly to avoid divisions in Tory ranks. But his efforts to avoid such rows may be leading him into another one.

Mr Bacon said last night that there was “a perfectly good precedent” for a post-ratification referendum in the one held by Harold Wilson on EEC membership in 1975, and he added that “I don't have a problem with it.”

Mr Brown has faced fierce criticism of his refusal to hold a referendum on the treaty despite a Labour manifesto pledge to hold one on the constitution. Some of it has come from within Labour ranks. And that continued yesterday when Norwich Labour MP Ian Gibson declared; “I think there will have to be a referendum. Many of us are not convinced that the constitution and the treaty are that different.”

The government has offered lengthy debating time in the Commons ahead of the treaty's expected ratification next year.

Signatories of the 'early day motion', tabled by Eurosceptic MP Bill Cash, claim that the “red lines” do not offer sufficient protection and point out that voters have not been given a direct vote on the European Union since 1975.

They add: “The reform treaty is a consolidation of the existing treaties into a merger of the European Community into a European Union involving substantial, fundamental, constitutional and structural change by the government's own criteria for a referendum.”