Nick Clegg on Monday called for a vote to “settle Britain’s relations with Europe once and for all” as he stepped up Liberal Democrat demands for a referendum on European Union membership.

The move was swiftly dismissed by opponents as an attempt to “paper over” his party’s split on Europe by “running away” from its alleged promise to back a plebiscite on the EU reform treaty. Mr Clegg has significantly increased the prospects of the Lisbon treaty – which is currently being debated in parliament – being passed into law by supporting the government’s decision against holding a referendum.