Tony Blair has never publicly commented on the EU president role
The UK has failed in its attempt to get Tony Blair chosen as the new president of the EU Council after the Belgian prime minister was handed the job.
Downing Street abandoned its campaign to put the ex-prime minister in the prestige job on Thursday after it was clear he did not have enough support.
But, in a surprise move, Labour peer Baroness Ashton was appointed to the new role of EU foreign affairs chief.
Gordon Brown said this "reinforced" the UK's place "at the heart of Europe".
"It will ensure Britain's voice is very loud and clear," he said.
Baroness Ashton is currently the EU's Trade Commissioner, a job in which Mr Brown said she had been "highly effective".
Mr Brown said Baroness Ashton - who will also become vice-president of the European Commission - would represent the EU on the world stage.
Little-known outside the UK and not a high-profile figure in British politics, Baroness Ashton was formerly leader of the House of Lords.
In choosing Baroness Ashton, Mr Brown said he had been determined to protect the UK's national interest in Europe.
Mr Blair had never publicly said he was in the running for the job of EU President - given to Belgium's Herman van Rompuy - despite vocal support from Mr Brown.
The prime minister said that his predecessor would have made an "excellent candidate" and that he did not "apologise" for backing him.
However, he said it had become clear that the job was destined for a centre-right candidate and that the nature of the post had changed - making it less suitable for Mr Blair.
'Defeat for PM'
The Conservatives and the Liberal Democrats welcomed the fact that Mr Blair had not got the job, saying he would have been a divisive figure.
"We did not agree with the Lisbon Treaty's establishment of these posts but they are now a fact," said shadow foreign secretary William Hague.
"We look to the President of the Council and the High Representative to ensure that the EU's business as an association of nation states is conducted efficiently."
"Gordon Brown spent a great deal of energy and political capital trying to secure the presidency for Tony Blair. The summit's result is a defeat for him."