Nigerian-British Shadow business secretary Chuka Umunna has withdrawn from the Labour party leadership contest, just days after throwing his hat into the ring, BBC reports
The MP, 36, said in a statement that he was not comfortable with the level of pressure and scrutiny that came with being a leadership candidate.
Mr Umunna also cited concerns about the impact of the bid on his family.
The BBC's Nick Robinson says Mr Umunna has been distressed by the level of scrutiny on him and his family.
He added that he understood there was no scandal that lay behind his decision to step aside.
A rising star of the party, Mr Umunna was first elected to Parliament in 2010 before joining the shadow cabinet.
He confirmed his candidacy for the Labour leadership via a post on his Facebook page on 12 May, saying the party under Ed Miliband had failed to appeal to enough voters in England.
But in a statement on Friday he said he had not found the leadership bid to be "a comfortable experience".
I understand that Chuka Umunna has told friends that "this is not right for me or people close to me. I'm human, the rest of my life is more important to me than politics."
The shadow business secretary has been distressed by the degree of scrutiny he, his family and his girlfriend have come under since he declared his intention to stand for the labour leadership.
I am told that this includes reporters waiting outside the houses of relatives late at night.
Friends of Mr Umunna deny that he is nervous of not getting the support of enough MPs to run for the leadership, they point out that he already has half the necessary names and that there are some weeks to go.
The shadow business secretary now wants to play a leading role in arguing that Britain should stay in the EU and does not rule out seeking the leadership in the future.
He said he thought he understood "the scrutiny and attention a leadership contest would bring", but added: "However, since the night of our defeat last week I have been subject to the added level of pressure that comes with being a leadership candidate."
The shadow business secretary said he had wondered if it was too soon for him to stand for the leadership, and "I fear it was."
He also cited concerns about the impact on "the rest of one's life" and those close to him.
"Consequently, after further reflection, I am withdrawing my candidacy," he said.
Mr Umunna said he would continue to serve as shadow business secretary and hoped to "play a leading role" in Labour's campaign to keep the UK in the EU during the forthcoming in/out referendum.
Commenting on the news, Labour former culture secretary Ben Bradshaw - who is rumoured to be considering running for deputy leader - said Mr Umunna was a "terrible loss" to the field.
He told the BBC's Daily Politics the Streatham MP had been the candidate the Conservative Party "feared the most".
"And if it's the result of pressure on an extended family or an extended group of friends, I think that's a very sad reflection on our political culture," he said.
Labour MP Chi Onwurah, - who has worked alongside Mr Umunna in the shadow business team - said she was saddened by the news.
BBC political correspondent Eleanor Garnier said the news was a "huge shock" as Mr Umunna had been seen as one of the frontrunners in the race.
She said Mr Umunna felt that due to the "sheer pressure" of the contest it was not the right time for him - or his family - to put himself forward.
Yvette Cooper, Andy Burnham, Liz Kendall and Mary Creagh have already thrown their hats into the ring for the Labour top job.
Candidates must secure nominations from 34 colleagues - 15% of the party's MPs - by 15 June to make it on to ballot papers, which will be sent to members in August ahead of the leader's election a month later.
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