By Owen Bennett-Jones
BBC News, Islamabad
Mr Ahsan has been a staunch critic of deposed President Musharraf
One of Pakistan's most prominent pro-democracy leaders, Aitzaz Ahsan, has accused a senior British diplomat of undermining his country's rule of law.
Sir Mark Lyall Grant was in Pakistan recently and reportedly urged the government to give President Musharraf immunity if he resigned.
Mr Ahsan said that any deal to give the president "safe passage" was wrong.
The British Foreign Office told the BBC it was working to avoid confrontation in Pakistan.
Mr Musharraf stepped down on Monday after nine years in power to avoid a move by the government to impeach him.
'Above the law'
As President of the Supreme Court Bar Association, Aitzaz Ahsan has emerged as one of the most effective and powerful pro-democracy leaders in Pakistan.
So his criticism of senior British Foreign Office official Sir Mark Lyall Grant, who recently visited Pakistan, is significant.
It's argued Mr Musharraf should not be given "safe passage"
The Pakistani press reported that Sir Mark urged the government in Islamabad to reach a deal with the president by which he would resign and thereby escape prosecution.
"It's the Brits who have stitched the deal," Mr Ahsan said.
"Mark Lyall Grant... won't put a single man, a Britisher or non-Britisher in England or in the United Kingdom above the law and yet he comes here and puts the president above the law.
"Today giving safe passage out to Musharraf is allowing safe passage in to the next man three years down the line."
He said that Mr Lyall Grant was a "key figure" in undermining the rule of law.
Mr Ahsan said that he wanted President Musharraf to be tried in Pakistan for abrogating the constitution when he sacked scores of judges last November.
He himself was put under house arrest for his involvement in efforts to restore Iftikhar Muhammad Chaudhry as the Chief Justice of the Supreme Court after President Musharraf suspended the constitution and removed him from the bench.
The British foreign office has responded to Mr Ahsan's statement by issuing a statement saying it had not prescribed a specific solution to Pakistan's political crisis.
It said that London was however keen that Pakistan found a way out of confrontation.
It is not the first time that Sir Mark Lyall Grant has played an active and controversial role in Pakistani politics.
Last year he was a key figure in persuading President Musharraf to drop a whole series of corruption charges against the then opposition leader Benazir Bhutto so that she could return to Pakistan and once again participate in the country's politics.