Former home secretary David Blunkett is to stand down from Parliament at the next general election, he has announced.
Mr Blunkett said it was clear that Ed Miliband would want "new faces in ministerial office and a clear break with the past" if Labour won next year's election as he informed his Sheffield Brightside and Hillsborough constituents of his decision.
Labour leader Mr Miliband said Mr Blunkett had been an "amazing asset" to the party who will be "hugely missed".
Mr Blunkett, 67, twice resigned from Cabinet posts under Tony Blair but told local party members that standing down was "by far the most difficult political decision I have ever made, in a lifetime of extremely difficult decisions".
He said: "Next year will see 10 years on the backbenches, five in opposition. Whilst I have been able to use the experience and the clout which came from having been a Cabinet minister for the benefit of the constituency in getting a hearing, contributing to policy and providing a voice for local people and for Sheffield at national level, it is clear that the leadership of the party wish to see new faces in ministerial office and a clear break with the past.
"For me, being in a position to make decisions and thereby make a difference, has always been paramount, and I hope in future to continue to promote our success and values, and to make a continuing contribution to public service and the social and voluntary sector."
He added that "there does come a time when a fresh approach and the energy that goes with it outweigh other considerations, and I believe that for the party and for the constituency, as well as for me personally, that moment has come".
Mr Blunkett, who is blind, was first elected as MP for the Sheffield Brightside seat in 1987 and served as education secretary, home secretary and work and pension secretary under Tony Blair.
He resigned as home secretary in 2004 after a visa application for ex-lover Kimberly Quinn's nanny was fast-tracked. An official inquiry found a "chain of events" linking Mr Blunkett to the speeding up of a visa application.
Less than 12 months later his return to the Cabinet as work and pensions secretary ended in resignation amid a row over his business interests.
Mr Blunkett said he was "privileged to be able to lead on ground-breaking policies" in education and the security of the nation after the 9/11 terror attacks in the USA in 2001.
"Many of the seeds I was able to sow, from welfare reform to lifelong learning and from the new challenge of cyber security to the debate on values and citizenship, are only now bearing fruit," he said.
"Above all this is a moment when we need to offer hope, a belief in government as a means of supporting people in making their own decisions and coping with unprecedentedly rapid change in an increasingly global political environment.
"Helping with the transitions of life, providing greater security and overcoming the fears generated by uncertainty, can only be achieved by a Labour government committed to giving a voice to those excluded from the power which comes with wealth and privilege.
"Ed Miliband is committed to leading Britain through the challenges ahead, to offering that hope and transforming our country in order to take on both the opportunities and pitfalls of globalisation, and to hear and respond to fears and concerns of men and women across the country."
Mr Blunkett's decision leaves a vacancy in a safe Labour seat, which he won with a 13,632 majority in 2010.
He is the latest former member of the New Labour-era Cabinets to announce his decision to quit the Commons in 2015, including his predecessor as home secretary Jack Straw.
Mr Miliband thanked Mr Blunkett for nearly 45 years of service as a councillor, MP and minister.
He said: "David Blunkett is a man whose commitment and determination have carried him to the highest positions in politics with one purpose: to serve the people of our country. He will be hugely missed."
Mr Miliband added: "He has been a friend to me during my time as leader. I have valued and counted on his advice and wisdom. Every Labour leader under whom he served would have said the same. He is Labour through and through.
"David can take great pride in all he has done to improve the lives of people in this country. He has been an amazing asset to the Labour Party and to Britain and I know he will continue to serve the country and the Labour Party with great distinction."Suggest a correction