Lord Sugar was appointed a peer by the last Labour government in 2009 Photo: AFP/Getty
Lord Sugar, the entrepreneur and Apprentice star, has quit the Labour Party after becoming disillusioned with its "negative business policies" and "anti-enterprise concepts".
The peer said that he repeatedly told the "most senior figures" in the party about his concerns over proposals should the party be elected under Ed Miliband's leadership, but they failed to act.
Lord Sugar said his resignation was accepted as the party had been "aware of my disillusionment for some time".
Lord Sugar took up his seat in the House of Lords in 2009 (PA)
He said: "In the past year I found myself losing confidence in the party due to their negative business policies and general anti-enterprise concepts they were considering if they were elected. I expressed this to the most senior figures in the party several times.
"I signed on to New Labour in 1997 but more recently, particularly in relation to business, I sensed a policy shift moving back towards what Old Labour stood for.
"By the start of this year I had made my decision to resign from the party whatever the outcome of the general election."
Lord Sugar said he informed the party of his decision on Friday and kept his intentions quiet during the election campaign rather than use them to "possibly damage" Labour's election chances.
He was initially appointed a peer by the previous Labour administration in 2009, but launched a scathing attack on the vision outlined during Mr Miliband's tenure.
In a statement posted on Twitter, Lord Sugar added: "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.
"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. There 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.
"I intend to continue in the House of Lords, representing the interests of business and enterprise in the UK. I will be making no further comment at this time."