Ballot papers have gone out in the three-week-long contest to elect a new leader of Britain's Labour party, following the resignation of Gordon Brown after his election defeat in May, DPA reported.
Five candidates are contesting the job, which is elected via a postal ballot of members, parliamentarians and trades union affiliates.
Voting ends on September 22, and the winner will be announced at the Labour party conference in Manchester on September 25.
Two brothers - David and Ed Miliband - are the frontrunners in the contest, in a fratricidal twist which has given the otherwise-bland contest some frisson in the past months' campaigning.
David Miliband, the elder sibling, served as foreign secretary in the last Labour administration, whilst Ed was energy secretary.
Whilst David is in the lead and the pollsters' favourite, as well as reportedly having the backing of former prime minister Tony Blair, his brother Ed has mounted a late surge.
In a complex knock-out alternative vote system, Ed Miliband could still win on second-preference votes.
The other candidates are former education secretary Ed Balls, former health secretary Andy Burnham, and backbench parliamentarian Diane Abbott.
Abbott, who is both the only woman and the only black candidate in the race, is the most left wing of the quintet, although she stands almost no chance of winning. Brown, who resigned as Labour leader after losing the May election, remains a parliamentarian. He has said he will not be publicly backing any candidate.
Attention toward the contest has partly been distracted by the imminent publication of Blair's memoirs, The Journey.
The book - to be published on Wednesday - has been widely trailed, with a setpiece hour-long interview on BBC TV. Earlier this month Blair announced the profits - several million pounds - would go the Royal British Legion, helping injured ex-service men.
As prime minister, Blair sent British troops to Afghanistan and to Iraq - the latter a highly-controversial decision from which many observers say Labour's support never fully recovered.