Britain's deputy prime minister Nick Clegg says David Cameron's veto of European Union treaty changes are bad for Britain and could leave it marginalised.
European leaders agreed last week to draft a new treaty, which will involve greater EU control over national budgets and automatic penalties for those whose deficits grow too large.
But the UK vetoed the plan after an opt-out on financial regulations was denied.
Mr Clegg blames France and Germany's unwillingness to agree and pressure from eurosceptic Conservatives for putting the Prime Minister in a very difficult position.
The director of the Centre for European Reform, Charles Grant, says Britain is the big loser and its influence will be reduced as a consequence.