Scandal-hit Liberal Democrat MP Mark Oaten is to stand down at the next general election.
Mr Oaten says he wants to change careers
The 42-year-old MP has ended speculation over his political future by announcing he will not contest his Winchester seat.
He was forced to quit the party's front bench in January after admitting a relationship with a male prostitute.
Days earlier married Mr Oaten quit his party's leadership contest citing a lack of support from colleagues.
The former Lib Dem home affairs spokesman has said he wants to change careers when he stands down and concentrate on development issues.
In a brief statement, he said: "I will continue to work for all my constituents both locally and at Westminster, where I also hope to focus on human rights and Third World development issues.
"At the time of the next election I will have served over 12 years as an MP and, having spoken with my wife Belinda, we feel it will be the right time for us to take on new challenges."
Harvey Cole, chairman of Winchester Liberal Democrats, said Mr Oaten's constituents would be "saddened" by his decision.
"Mark told me last week he would be leaving parliament at the next general election.
"I, together with the executive committee, will be very saddened by his decision but we fully understand the pressure on him which has lead to it.
"We fully support Mark's desire to switch his impressive energy from the limelight of the front bench to an interest in the vital problems of the Third World.
"We know he will continue to be an outstanding champion for all his constituents and remain the most effective MP Winchester has ever had".
Mr Cole added that the local party would now select two candidates as the constituency is due to split into Winchester and the Meon Valley before the next general election.
Mr Oaten was seen as one of the Liberal Democrats' fastest rising stars but he was forced to quit frontline politics after the News of the World published details of his relationship with a rent boy.
Both Mr Oaten and his wife Belinda, who have two children, have given interviews about how they have tried to rebuild their lives following the revelations.
In an article for the Sunday Times, Mr Oaten said his fall from grace was prompted by a mid-life crisis brought on by his rapid hair loss.
He also said he did not enjoy life in the Westminster village, but had not been able to get off the political treadmill and quit the frontbench.
He explained the pressure of work had distanced him from his family and he had sought psychiatric help.
Mr Oaten's Conservative opponent at the last general election George Hollingbery said Mr Oaten had been "under some pressure" since the allegations emerged.
"There has been speculation that he should step down, so I'm not surprised.
"The recent district council elections here in Winchester also demonstrated that voters did not like what Mark did and voted his party from power. I wish him and his family the best of luck in their future.
"There is no doubt Mark has been a diligent MP for Winchester, but politically his time was over."
Liberal Democrat chief whip Paul Burstow said: "Mark has always been a hard working MP representing the interests of his constituents since first being elected to Parliament in 1997.
"Winchester will continue to benefit from his hard work, both locally and at Westminster."