Chuka Umunna
Chuka Umunna has dropped out of the race to be the next Labour leader Reuters

Chuka Umunna shocked the Labour Party with his sudden withdrawal of his leadership bid, just three days after putting himself forward as a contender.

Speculation has been rife as to the real reasons behind his quick exit including that of the Sunday newspapers preparing an "expose" on him, despite his aides denying such rumours.

The suave shadow business secretary, who had the potential to go all the way and become the party's leader, and even prime minister one day, blamed the impact of press intrusion on his family and friends – including his lawyer girlfriend Alice Sullivan and her 102-year-old grandmother – which had become an "uncomfortable" experience .

Ex-culture secretary Ben Bradshaw told Sky News the MP's family had been doorstepped by the media near his south London constituency of Streatham.

"I understand it involved an elderly mother and other relatives," he said. "It's a sad fact of our political and media culture in Britain that people who want to serve democracy and want to serve in public office are subjected to this level of scrutiny."

But other commentators say he was not blaming the media but the issue was "more about whether he was ready for it".

Some cynics believe the Sunday press had "lethal dirt" on the former garage DJ, which prompted him out of the race instead. But sources close to him say his withdrawal was not connected to any negative story due to appear over the weekend.

Other theories suggest his immediate withdrawal was connected to him planning to run for mayor of London following accusations that he does not appeal to Labour's core working-class voters. But this has been refuted by the Sun's politics reporter, Tom Newton Dunn, who was informed by Umunna's aides that the mayoralty was not the politician's intention.

Another argument is he would prefer to opt out of the leadership contest at this stage before entering it again in a couple of years, which could put him in a better position to be the man to lead Labour to victory in 2020.

The 36-year-old now leaves the race open for Andy Burnham, Yvette Cooper, Liz Kendall and Mary Creagh to be Ed Miliband's successor.

Political correspondent Michael Crick tweeted Umunna may have faced problems of competing with nominations from Blairite MPs and "was getting very crowded - with Kendall, Creagh & maybe Hunt also running".

Umunna once got into trouble after tweeting his disdain about a lack of places to go in the West End – referring them to be full trash and C-listers.

His office was also known for amending his Wikipedia page to include a reference of being one day the "UK's Barack Obama".