MP for Stalybridge and Hyde James Purnell has admitted "I just don't want to be an MP any more" after deciding to quit front-line politics.

The former cabinet minister, once tipped as a future Labour leader, said he had tired of Westminster life after nearly two decades.

In his first interview after leaving the cabinet, the MP told the M.E.N there had been no 'plot' and he had acted purely out of conviction.

The MP, who will remain in post until the next general election, said it had been a 'tough decision' to stand down.

He said: "I am sad to be leaving, but it is right. The thing I am proudest of is the rebuilding of schools in Tameside. It is an example of a really huge difference we have made.

"Nationally, it might be the youth grants for the young unemployed."

Asked what he would do next, Mr Purnell said: "I don't want to jump straight to the next thing but it will be something in public service."

Mr Purnell went straight from university to work for Tony Blair.

Announcing his decision to quit parliament he said: "The office I am in now is just round the corner from the one where I started. I don't want to continue. I just don't want to be an MP any more."

Last June he sent shockwaves round Westminister when, in a letter resigning his post as work and pensions secretary, he called on Gordon Brown to stand down.

Mr Purnell said he believed Labour stood a better chance of winning the next election with a different leader.

The move was expected to unseat the prime minister – but other 'big beasts' refused to follow suit, and Mr Brown survived.

Mr Purnell – who has been plagued by rumours he might defect to a different party – told the M.E.N last night he had not 'fallen out of love' with Labour.

"I hope that Gordon proves me wrong and wins the next election," he said. "I want to do everything I can to help.

"I am going to continue with my role at [think-tank] Demos and hope I can play a role helping to contribute to ideas the party takes up."

Mr Purnell was a researcher for Tony Blair while studying at Oxford, and became a Downing Street special adviser in 1997.

He was elected in Stalybridge and Hyde in 2001 and entered cabinet as culture secretary in June 2007 at the age of 37.

He was promoted to work and pensions secretary the following January. He became increasing disillusioned with Mr Brown’s premiership, and eventually quit as Labour recorded a disastrous performance in local elections.

In his resignation letter, he called on Mr Brown to 'stand aside to give our party a fighting chance of winning'.

"It has been a real privilege to represent Stalybridge and Hyde," he said.

Peter Robinson, chairman of the Stalybridge and Hyde Constituency Labour Party, said: "Over the past nine years James has been an outstanding MP, who has been instrumental in bringing many benefits to the people of Stalybridge and Hyde.

"We understand completely the reasons for James’ resignation and we wish him every success in the future."