Labour has taken another high-profile blow after Lord Sugar dramatically announced his plans to quit the party because of Ed Miliband's shift towards Old Labour-style policies.
The Apprentice star revealed that he lost confidence in the party because of their "negative business policies", despite expressing his concerns to the "most senior figures in the party several times".
"In the past year I found myself losing confidence in the party due to their negative business policies and the general anti-enterprise concepts they were considering if they were to be elected. I expressed this to the most senior figures in the party several times," Sugar said.
The multimillionaire said he was brought into the party by Gordon Brown during the rise of New Labour, which saw the left-of-centre party shift to the right in a bid to win votes.
"More recently, particularly in relation to business, I sensed a policy shift moving back towards what Old Labour stood for," Sugar added.
The entrepreneur explained that he has made his decision to leave the party at the start of 2015, whatever the outcome of the general election.
But Sugar disclosed that he decided not to make or announce the move in the run-up to the general election because he wanted to stay loyal to Labour.
"However, I am a loyal person and rather than use my decision to possibly damage the party's chances in the election, I decided, as a relatively high-profile individual, to keep my intentions quiet for the duration of the campaign," he said.
"In the past few weeks I have declined hundreds of media requests to talk about the proposed policies of the party, particularly in relation to business, and instead opted to remain quiet. I have no wish to stick the boot into the party.
"These are many good people in Labour working hard every day to serve the public, and I wish them all the best of luck. I am grateful for all the experiences being a member of Labour has brought me."
Sugar, who was appointed to the House of Lords as a life peer in 2009, said he would carry on in the chamber and represent "business and enterprise".
Mandelson's scathing attack
The announcement comes after former business secretary and New Labour architect Lord Mandelson also attacked the party on similar grounds.
The Labour grandee argued that Miliband had made a "terrible mistake" by ditching New Labour and claimed the former leader should have modernised the project.
"We were sent off in 2010 on a sort of giant political experiment in which we were sent out and told to wave our fists angrily at the nasty Tories and wait for the public to realise how much they had missed us," he told the BBC's Andrew Marr show.
"They weren't missing us. They didn't miss us. Instead they ripped the stripes off our shoulders."
The attacks against Miliband's premiership come after the Tories secured a shock majority in the House of Commons and Labour were nearly wiped out in Scotland at the general election.
Miliband resigned as leader after losing 24 MPs and said he took full responsibility for the crushing defeat. The scale of the loss prompted Labour former Home Secretary Alan Johnson to warn that it could take 10 years for the party to gain power again.
Meanwhile, the likes of Chuka Umunna and Tristram Hunt have set out their stalls for the Labour leadership. But so far only Leicester West MP Liz Kendall has officially declared her intention to run for the top job as others shadow box.