Former foreign secretary David Miliband officially launched his bid to lead the Labour party today.

He announced his intention to run for the leadership last Wednesday with a press conference but formally launched it in his South Shields constituency today.

In a speech titled Next Labour, he said the party had suffered a “serious defeat” in the election and that Labour had been sent for “serious rehabilitation” by the electorate.

Mr Miliband, calling himself an “idealist”, said that what mattered now was “next Labour”, not New Labour.

He said: “The Blair/Brown era is over. I am not interested in politics defined as Blairite or Brownite. New Labour isn’t new any more. We learn from it; we benefit from it; we seek to emulate its successes but not repeat its mantras.

“We need new ideas, and new ways of doing politics.

“New Labour did fantastic things for the country. But now we are out of power, what counts is next Labour. Listening, idealistic, open, engaged, thoughtful, radical, decisive, Labour.”

He mentioned gay equality several times in the 25-minute speech, saying that no political party now dared to oppose gay rights and calling civil partnerships the result of the pairing of individual freedom and social justice.

Mr Miliband also promised his spokeswoman Lisa Tremble would be named in order to tackle negative and unattributable briefing against other candidates.

As yet, only Mr Miliband’s younger brother Ed Miliband has declared himself a rival for the leadership.

Mr Miliband called his brother a “great talent” and said he was “very proud” of him.

At the end of his speech, he said that political rivalry would not harm his family.

He said: “Our family is more important than politics and we are absolutely determined that it won’t get in the way. Ed is extremely talented and has made his own decision to run.

“He is going to be a brother I love at the end of the campaign, whatever happens. My mum is not the abstaining type but she’s abstaining on this one.”

Former schools secretary Ed Balls is also expected to declare his candidacy, along with former health secretary Andy Burnham and John Cruddas.

Jack Straw, Alan Johnson and Yvette Cooper have all ruled themselves out of the race.

Former equality minister Harriet Harman, who is the party’s caretaker leader after Gordon Brown resigned last week, has said she is content with being deputy leader.

Earlier this month, a poll of nearly 1,000 PinkNews.co.uk readers placed Mr Miliband senior as the most popular choice to take over from Gordon Brown.

Thirty-one per cent of our sample backed him for the Labour leadership, followed by 14 per cent for Mr Johnson and 11 per cent for Ms Harman.