Deputy Prime Minister Nick Clegg hosts a meeting of his liberal allies from around Europe in London on Monday to promote his agenda of re-engagement with the European Union after the UK vetoed an EU treaty in December.

Dutch Prime Minister Mark Rutte, EU Economic and Monetary Affairs Commissioner Olli Rehn and German Economy Minister Philipp Roesler are among the senior liberal figures joining Clegg at the mini-summit in the British capital.

Prime Minister David Cameron set the country on a separate orbit from the 26 other members of the European Union at the end of last year when he refused to sign a treaty on measures to help resolve the euro zone debt crisis.

Cameron, Conservative head of a coalition government with Clegg's Liberal Democrats, withheld his support after failing to win protection for Britain's important financial services sector.

His veto of the treaty, which left Britain isolated within the EU, won Cameron plaudits from increasingly influential euro sceptic legislators in his Conservative party, but dismayed the pro-European Liberal Democrats.

Clegg, who told Cameron the move was bad for Britain, has promised to redouble efforts to engage with Europe to prevent Britain losing influence in Brussels.

This (meeting) is one clear part of that, said a spokeswoman for Clegg.

But Douglas Carswell, a prominent Conservative euro sceptic legislator who wants Britain to hold a referendum on leaving the EU, said the gathering would serve little purpose.

There will be a lot of mushy goodwill and talk of re-engagement, but does that mean that our government will be able to safeguard our national interest? he told Reuters.

At the meeting liberal ministers and EU commissioners will discuss the euro zone crisis, measures to boost growth in the bloc's fragile economy and the future of the EU's multi-billion euro budget, a frequent source of contention between member governments.

The summit is formally a meeting of the European Liberal Democrats, an association which groups 55 liberal parties across Europe.

(Reporting by Tim Castle; editing by Tim Pearce)