Jemima Khan, the ex-wife of Pakistani cricketer-turned-politician Imran Khan, has joined a protest outside Pakistan's High Commission in London.
Ms Khan called on Gen Musharraf to resign
They were protesting against the state of emergency established in the country by President General Pervez Musharraf since 3 November.
About 150 demonstrators called for the release of all political prisoners.
Mr Khan was arrested last week along with thousands of other political opponents of General Musharraf.
Ms Khan, 33, who helped set up the Free Pakistan movement with the help of lawyers, journalists, doctors and other professionals, attended the demonstration with the youngest of her two sons.
The eight-year-old boy held a picture of his father with the words "Release Imran. Release my Aba" - which is Urdu for father.
Ms Khan handed over a petition to the High Commission alongside Supreme Court lawyer Hina Jilani and Dr Aamer Sarfraz.
She told reporters: "I think it is time for Musharraf to resign.
"It's gone too far, he needs to go, but there are other things we are calling for: for the judiciary to be restored, for the press to be freed, for the conditions of democracy to be restored, for all political prisoners to be released, and for the right to protest.
She added: "We have to protest here because our friends in Pakistan are being arrested for protesting in Pakistan.
"I'm doing this because Imran and my friends in Pakistan have asked us to make noise here because they are not able to in Pakistan, but I am doing it because I care about Pakistan and I care about the issue of democracy and human rights."
'Martial law imposed'
She called on the British government to continue to put pressure on the general to resign.
She said her ex-husband's sisters, his female cousins, and an elderly aunt had also been detained after taking part in protests in Pakistan.
Respect MP George Galloway told the crowd he held Pakistan's two highest awards, but he also had the honour of being "a friend of the hero Imran Khan".
He added: "I say shame on the government represented by the high commission behind us."
Political commentator Tariq Ali said: "This latest martial law that has been imposed, what is the reason for it?
"The impression given by the government and in Musharraf's pathetic, incoherent broadcasts is that we had to do this because we are fighting terrorism. But is Imran Khan a terrorist? The terrorists are people who thrive on martial law."
Gen Musharraf declared emergency rule earlier this month, saying Pakistan was under threat from militants and the judiciary.