David Lepper is to quit as Labour MP for Brighton Pavilion at the next general election.
The former schoolteacher, now 61, was the first Labour candidate ever to win the formerly safe Tory seat when he beat the Solicitor General, Sir Derek Spencer, in 1997.
Since then he has held the seat at the elections of 2001 and 2005. He has a majority of 5,030.
Mr Lepper is telling party workers this week of his decision to quit. He said: "By the time the next election comes, I will have been nearly 30 years in political life.
"Now is the time for me to make way for the next Labour MP for Brighton Pavilion."
Mr Lepper first stood for Brighton Council in 1979 but won his seat in a by-election the following year.
Within four years he was leader of the opposition and in 1986, when his party took control, he became the first Labour leader in the council's 130-year history.
After that, Mr Lepper concentrated on trying to win the Pavilion Parliamentary seat which had been considered a Tory stronghold since 1950 with long-serving MPs such as Sir William Teeling and Julian Amery. His win came during the Labour landslide of 1997 which also saw Kemptown and Hove fall to Labour.
He has built a reputation as a good constituency MP who helps thousands of people each year. His interests in Parliament have included ending poverty, helping wildlife, improving the environment and stopping discrimination.
Mr Lepper said he was glad the Labour Government, with projects such as the New Deal, had helped to stop what he called the "cycle of despair" for many deprived people.
He was pleased to have played a part in legislation which led to the minimum wage and leasehold reform.
The MP also pressed hard for the repeal of Section 28 of the Local Government Act which ended discrimination against gay and lesbian people. He lobbied for civil partnerships.
Mr Lepper fought for the creation of the South Downs National Park and for business improvement districts. One is being established in Brighton.
He has also been active in the campaign to outlaw violent pornography following the Jane Longhurst case in Brighton.
The MP said: "I have disagreed with Tony Blair on some aspects of foreign policy but I am proud to have been in a Government led by him."
He was particularly pleased with progress in helping the developing world and in action to tackle climate change.
Mr Lepper said: "There is a lot more to do as I expect to remain an MP for the next two or three years."
He will back Labour candidates in next year's council elections in the hope the party will regain control of the authority, which has no overall majority.
His wife Jeane is a member of the council, representing Hollingbury and Stanmer. They have two grown-up children.
Mr Lepper hopes to pursue other interests including films.
He declined to comment on who might be selected to fight in his place at the next election.
Peter Freeman, chairman of the Brighton Pavilion Labour Party, said: "We want as big a field as possible."