Amjad Hussain broke down on TV under the strain

Amjad Hussain said he would look at claims that his brother, Mirza Tahir Hussain, was attacked for making an illicit phone call to the BBC.

He said mobiles were prohibited to death row inmates and there had been suspensions in the wake of the call.

His trip coincides with a visit to Pakistan by Prince Charles.

Mirza Tahir called the BBC's Asian Network from his cell and appealed to Pakistan's President Pervez Musharraf to pardon him.

He also thanked Prime Minister Tony Blair and the Prince of Wales for their interventions on his behalf.

Mirza Tahir Hussain pleaded for his life from his cell

Amjad said he was told last weekend that inmates at the prison had alerted the press that his brother "was taken away for questioning and was manhandled" after the call.

"There were suspensions and the prison was visited by the director of prisons because this was a massive breach of security, even though he gave a very dignified interview," he said.

Amjad emphasised that the claims remained "unsubstantiated" but said the British High Commissioner would be looking into them during a visit to his brother on Thursday.

He was speaking after a Westminster Hall debate in which Greg Mulholland, MP for Leeds North West, urged President Musharraf to use his authority to have the death sentence commuted.

Mirza Tahir, 36, was convicted of murdering taxi driver Jamshed Khan in a remote area of Pakistan in 1988 - although he insisted he acted in self-defence.

The country's High Court later quashed his conviction, but he was retried under religious laws and sentenced to death.

His execution was commuted from 1 November until New Year's Eve after representations from Mr Blair and the Prince - who is due to begin an official visit next week.