Will Gordon try to do next what Tony did previously?

Tony Blair promised a referendum on the EU Constitution in order to cancel out a popular Conservative policy at the last General Election. According to The Sunday Times it is rumoured that Gordon Brown might offer a referendum not on signing up to the EU Treaty but on whether the UK should remain in the EU itself, this will be done in an attempt to open up the splits within the Conservative party on Europe. Whilst the Conservative Party could hold together calling for a referendum on the EU Treaty and could probably stay together if such a referendum was called, I can not see the Ken Clarke and John Redwood wings of the party holding together in a referendum on EU membership.