Mirza Hussain has been in jail for 18 years

Mirza Tahir Hussain, 36, was due to be hanged on 3 August after his conviction for killing a taxi driver in Pakistan.

Hussain's brother Amjad and about 150 human rights activists and supporters staged a demonstration at the Pakistani Embassy in London on Thursday.

Amjad Hussain said the new delay was "the continuation of a nightmare".

"This is psychological torture, it's die another day," he said.

"They've offered nothing new, they've got no regard for human life at all. This is just an extra month of torture.

"We've been going through this for the last 18 years and the effect on the family is devastating."

'Horribly real'

A spokesman for the High Commission confirmed that President Musharraf had given the stay of execution, which will give more time for financial negotiations with the dead man's family, which could lift the death sentence.

Mirza Tahir Hussain claims he killed the taxi driver in self-defence. After several trials, Pakistan's High Court threw out his guilty verdict, citing flawed evidence.

But he was then retried by an Islamic court, which sentenced him to death.

During Thursday's demonstration, his brother delivered a letter to the High Commission calling on President Musharraf to commute the sentence and for the Pakistani authorities to urgently re-examine the case and conviction.

It was signed by members of Hussain's family and politicians from all parties including the family's Liberal Democrat MP, Greg Mulholland, and the Leeds MP and Secretary of State for International Development Hilary Benn.

'Miscarriage of justice'

Mr Mulholland said: "There is a horribly real possibility that Mirza could be executed unless urgent action is taken.

"I am sure that President Musharraf would not want a man to be executed where the conviction is so obviously unsafe and we are asking him to intervene to overturn this judgement before a terrible miscarriage of justice takes place."

Fair Trials Abroad director Catherine Wolthuizen said: "We are pulling out all the stops to save Mirza's life and secure his freedom.

"Sentenced to death on the basis of fabricated evidence and double jeopardy, his execution would be an appalling travesty of justice."