Voting for a new leader of Britain’s Labour Party sees one of two brothers tipped to win an election overshadowed by two heavyweights from the past – Tony Blair and Gordon Brown.

The contest was triggered when Mr Brown resigned after May’s general election at which Labour lost power for the first time in 13 years, making way for a coalition government under David Cameron of the centre-right Conservatives.

Ballot papers are being sent out today to around 160,000 Labour Party members, who have a third of the votes, as well as Labour lawmakers in the British and European Parliaments who have another third, and trade unionists who get the final chunk.

The result will be announced on September 25, the day before Labour’s annual conference begins in Manchester, northwest England.

The favourite to take over from Mr Brown is former Foreign Secretary David Miliband. The 45-year-old is nicknamed “Brains” for the wonkish skills which saw him serve as a top policy advisor to Mr Blair, to whom he remains close.

But David Miliband is facing a strong challenge from his younger brother Ed.

Aged 40 and seen as more charismatic than David, Ed was one of Mr Brown’s key advisors in the Treasury – when Brown was Blair’s Finance Minister – and later became Brown’s Energy Secretary.

The other candidates are pugnacious former Education Secretary Ed Balls, veteran left-winger Diane Abbott and youthful former Health Secretary Andy Burnham.

According to a projection last week for leading Labour blog Left Foot Forward, David Miliband has 36 per cent of first-preference votes, Ed Miliband has 31 per cent, while the other have 11 per cent.

Politics run deep in the Miliband family. David and Ed’s late father was a famous Marxist thinker, Ralph Miliband, while their mother Marion was an activist and academic but has not said whom she will be supporting in the election.

Both brothers insist the contest will not cause a rift in the Miliband household.