Margaret Beckett, the Foreign Secretary, has written to President Musharraf of Pakistan asking him to commute the death sentence of a Leeds man due to be hanged for murder.

Mirza Tahir Hussain, who has dual British-Pakistani nationality, was convicted of shooting dead a taxi-driver in Rawalpindi in 1988, but has always denied murder.

Hussain, who was brought up in Britain, was just 18 at the time of the killing, which happened during a holiday to visit his family. On his second night in Pakistan, he took a taxi to his family village but says that the driver, Janshir Khan, stopped the car and tried to sexually assault him.

During the struggle, Hussain says, the driver produced a gun, which went off, fatally wounding him. Hussain then drove the car and driver to the first police station.

Hussain has been in jail for nearly 18 years but after his conviction was quashed and reinstated twice, his stay of execution is due to run out on June 1, two days before his 36th birthday.

A Foreign Office spokesman said that Mrs Beckett was "asking President Musharraf that he agree to commute the death sentence to an appropriate term of imprisonment". He said that the letter was "on its way" to the Pakistani leader.

Another Government official said that the "exceptional" appeal was made on humanitarian grounds, considering the severity of the sentence and the time that Hussain has already spent in prison. He said that it also refers to Britain’s long-standing opposition to the death penalty and mentions Tony Blair's interest in the case.

Hillary Benn, the International Development Secretary, has also written to the Pakistani President in his capacity as Hussain's local MP. Hussain has also been backed by groups such as Amnesty International and Human Rights Watch, who say that he is the victim of a miscarriage of justice.

Pakistan’s Foreign Ministry confirmed that a request had been received from the British Government, but said that Hussain was sentenced to death after a thorough judicial process.

"The judicial legal system is taking its course. The sentence has been upheld by the highest court in Pakistan," said a spokeswoman, Tasnim Aslam.

"He is on death row. The date for his execution is due to be announced on June 1," added Mohammad Arash, assistant superintendent at Adiala jail in Rawalpindi, where Hussain is being held. "Under the law, the President cannot commute his sentence, only the relatives of the deceased could forgive him."

Mr Musharraf has already dismissed a mercy petition by Hussain, who was sentenced to death by a lower court in 1989 for murdering taxi driver Janshir Khan in Rawalpindi, a garrison town adjoining Islamabad.

The death penalty was later overturned by a higher court but then reinstated by Pakistan’s top Islamic court. Subsequent appeals also failed.

The Islamic court got involved because the case was registered under Pakistan’s medieval-style Hudood laws, an Islamic code of justice that human rights groups have frequently criticised.

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