David Cameron, leader of Britain’s opposition Conservative party, pledged on Monday that his move to create an anti-federalist grouping in the European parliament would not fracture relations with other mainstream centre-right parties in Europe.

“Yes, we’re in a party that wants reform in Europe . . . and yes, we still want that referendum on the European constitution, but we’ll never turn our backs on Britain’s obligations and the partners that we have in Europe,” Mr Cameron said.