Altaf Hussain, who once worked as a cab driver in Chicago, founded his Muttahida Quami Movement (MQM) in 1984 to represent the mohajirs – Muslim refugees who went to Pakistan from India on partition. The party went on to run the port city of Karachi with an iron grip while facing severe criticism from opponents who accused it of carrying out violent intimidation.
Mr Hussain left Pakistan after a warrant was issued for him in connection with a murder. He arrived in Britain in 1992 for a kidney operation and has stayed here ever since acquiring UK citizenship. The party's "international secretariat" is housed in a red-brick office block opposite a supermarket on Edgware High Street in north London.
Mr Hussain has been accused of directing attacks against political opponents while sitting in London. At the same time he forged a political alliance with General Pervez Musharraf and is said to be in regular telephone contact with the Pakistani leader. The party insists it is secular and liberal and in the forefront of the "war on terror" against Muslim fundamentalists.
MQM was accused of sparking the violence in Karachi in May when gunmen opened fire on supporters of the Chief Justice Iftikhar Muhammad Chaudhry; 42 people were killed. The security forces were accused of standing by and allowing MQM members to carry out attacks. Mr Hussain, however, denied the charges, saying that his members were victims and pointing out that 13 of them have been killed. Dr Farooq Sattar, the head of the party in Pakistan, said: "There is a conspiracy against us."
The British government is said to have liaised with Mr Hussain and the MQM recently in an attempt to ensure the safety of Benazir Bhutto when she returned to Pakistan to take part in the elections. In the event, she was the target of a massive bombing within hours of arriving in the country.