Both Germany and the Netherlands have warned they do not want the UK to slide out of the EU, ahead of David Cameron's planned showdown with European leaders tomorrow.
The Prime Minister has vowed to oppose Jean-Claude Juncker - the man many EU countries back for the job of European Commission president -"until the end".
No 10 sources suggest the UK's is braced for a backlash, insisting his position is not a bargaining chip but a point of principle.
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Earlier this week, former Prime Minister Sir John Major suggested that after humiliating a British Prime Minister EU leaders "often seek ... to make that right".
But yesterday, a Downing Street source said: "This is not about using principles as a bargaining tool."
Coalition tensions over the state of the UK's reputation in Europe bubbled to the surface yesterday.
Business Secretary Vince Cable went public with his criticism of Mr Cameron's handling of the row, which he said had damaged Britain's influence in Brussels.
The Prime Minister has cross-party support for his bid to block the appointment of Mr Juncker, who is seen by the UK as an ultra-federalist, but some Liberal Democrats are concerned by the Prime Minister's tactics.