David Cameron has been warned by Angela Merkel, the German Chancellor, that the Conservative Party faces isolation if he presses ahead with his plan to leave Europe's main centre-right grouping.
In a letter to the Tory leader, Ms Merkel suggested his party would walk into Europe's political wilderness if it quits the European People's Party (EPP-ED), the biggest single group in the European Parliament.
She urged him to think again about the move, which he promised during his campaign to win the Tory leadership on the grounds that the EPP-ED is too supportive of EU integration.
Ms Merkel said: "I look forward to good and intensive co-operation with you, and in particular within the framework of the EPP-ED."
Yesterday, Mr Cameron kept his distance from centre-right leaders by staying away from their traditional meeting before the summit of EU countries in Brussels. Instead, he visited Belfast, which went down badly at the Brussels meeting.
Last night, he made clear he would stick to his plan. His spokesman said: "David Cameron... believes the best thing is to leave the EPP-ED and create a new group that shows the way forward for the EU."