Ex-Labour leader and outgoing EU commissioner Neil Kinnock looks set to take a leading role in a referendum campaign on the European constitution.
Kinnock will throw his weight behind Britain in Europe
Mr Kinnock, fellow commissioner Chris Patten, and ex-Lib Dem MEP Nick Clegg are to join the board of Britain in Europe.
The news will be seen as a boost for the pro-European cause which enthusiasts feel has been dented by the UK staying out of the euro.
"To influence we must be properly in," Mr Kinnock said.
He added: "There is no such thing as outfluence."
Mr Kinnock's job will be seen as bid to shore-up pro-European support on the Left of the political spectrum.
Ex-Hong Kong governor Mr Patten, as a former Tory chairman, will appeal to pro-Europeans on the centre-right.
Mr Kinnock said: "I'm pleased to be joining the board of Britain in Europe. The reasons are basic: Economically, socially, politically and culturally the UK and its people have needs and interests which are profoundly similar to those of the rest of Europe."
He accused "Europhobes" of obscuring and distorting the truth about the EU.