BRUSSELS:The British premier Gordon Brown abandoned his support for Blair shortly before a dinner of EU leaders at an emergency summit in Brussels tonight.

But Brown appears likely to secure for his former cabinet colleague Cathy Ashton, the current European trade commissioner, the key post of high representative for foreign policy.

Herman Van Rompuy, the centre-right Belgian prime minister, remains the frontrunner to assume the presidency, which is created by the recently ratified Lisbon treaty. Germany and France have voiced support for Van Rompuy, although EU leaders are facing a lengthy night of horse trading in Brussels because there is irritation among some eastern European states at what they regard as outdated and high-handed pressure from Paris and Berlin. The Dutch prime minister, Jan Peter Balkenende, tonight ruled himself out as a candidate for the presidency.

As EU leaders embarked on their negotiations, British government officials were pressing ahead with what is being described as “Plan B”.

This is to win for Britain either the new post of high representative for foreign policy or a major economic portfolio in the European commission.

Brown moved on to “Plan B” after making a final push for Blair at a meeting of centre-left leaders in Brussels shortly before the summit. To nobody’s surprise, it became clear that Blair enjoyed no support in the group. At the meeting Brown pulled the Blair nomination off the table and proposed Ashton for high representative instead.

The biggest blow to Blair came when it became clear that centre-right leaders, such as Angela Merkel from Germany and Nicolas Sarkozy from France, were determined that a member of their grouping should assume the post. It was also clear that EU leaders wanted a chairman rather than a presidential figure.

Blair is not surprised that he failed to secure the post because he was aware of the “direction of travel” when he telephoned a series of EU leaders.

It is understood that he would have been unsure of taking the post when the Swedish government, which holds the rotating EU presidency, indicated in a paper on Wednesday that the president would have little or no role in foreign affairs.

This appeared to run counter to the Lisbon treaty, which said the president would oversee foreign policy in conjunction with the high representative.