Emma Reynolds, MP for Wolverhampton North East and Shadow Secretary of State for Communities and Local Government, has also announced that she will return to the backbenches.
The Leicester West MP Liz Kendall has lost out on the Labour leadership to Jeremy Corbyn. Mr Corbyn thanked Liz for her friendship during the campaign - he said that she always stood up for what she believed in.
Tom Watson thanks his family of supporters in West Bromwich East in his acceptance speech after being made Deputy Leader of the Labour Party.
Tom Watson MP for West Bromwich has won the contest to the deputy leader of the Labour Party.
Labour leadership candidate Liz Kendall has arrived for the announcement of the poll result.
She was met by an applauding group of supporters, but the welcome was rather more muted compared with the chanting crowd who mobbed Jeremy Corbyn a few minutes earlier.
Liz Kendall has trailed behind the other candidates in the polls throughout the campaign.
Turnout in the Labour leadership election was 76.3 per cent, according to party sources.
Around 550,000 people were registered to vote.
Labour leadership favourite Jeremy Corbyn was mobbed by fans who shouted and cheered as he arrived for the results announcement.
Corbyn, the surprise frontrunner in the contest, was met by a large crowd of 'Team Corbyn' supporters, who shouted "good luck Jeremy" and waved placards bearing his face.
The results are due to be announced at 11.30am.
Tom Watson said he had been thinking about quitting as Labour election co-ordinator "for a few months", because he found the post very tiring and felt unable to speak out on issues of concern.
He told BBC Radio WM: "We have had all this fuss over Falkirk and I just thought to myself, if I am getting into the story and not being useful any more for Ed, then it's time to move.
Asked about the details of what had happened in Falkirk, he said: "I really don't know about that. One of the things I did on Falkirk was keep out of that process, because there's an employee of mine who was a candidate.
"I know this works - people put two and two together and very often get five, but that's not the reason I have gone. The Falkirk thing crystallised in my mind how difficult it would be for me to stay in the post."
He added: "I've had an unusual journey in politics. There are some people who have never quite forgiven me for resigning in 2006 under Tony Blair and I accept that completely. What I don't want to be is a problem for Ed Miliband, so going to the backbenches is the best thing.
"I want him as Prime Minister and he has got my full support."