UK police documents obtained by the BBC list more than 70 London bank accounts related to a Pakistani party being investigated for money-laundering.
Twenty-six are in the name of MQM leader Altaf Hussain. UK-based party officials are waiting to hear if they will face money-laundering charges.
Six British detectives were recently in Pakistan seeking co-operation in the alleged money-laundering case.
The MQM has said Scotland Yard's claims about the bank accounts are baseless.
British police have been investigating the MQM, one of Pakistan's main political parties, for several years but the pace of their investigations has picked up markedly since a meeting in London in April between Pakistan's Interior Minister, Chaudhry Nisar Ali Khan, and Home Secretary Theresa May.
The Scotland Yard documents, which include details of both open and closed bank accounts, were submitted to Pakistan's Federal Investigations Agency (FIA) as part of a British request for assistance.
Scotland Yard has declined to comment on the documents.
The UK's Crown Prosecution Service is already considering whether leading MQM officials should be charged with money-laundering offences but police say that does not stop them making further inquiries.
"The investigation continues and any further relevant information would be discussed with the CPS," said a spokesperson at Scotland Yard.
Who is Altaf Hussain?
- Born in Karachi in 1953 to a middle-class family; studied pharmacy at university
- Formed MQM party in 1984 to represent Mohajirs - descendants of Urdu-speaking Muslims who migrated from India to Pakistan at the time of partition
- Requested political asylum in Britain in 1992, later gaining British citizenship; continues to run MQM from London
Altaf Hussain has lived in self-imposed exile in London for more than 20 years.
With 24 members in the National Assembly, the MQM is a dominant force in the politics of Pakistan's largest city, Karachi.
The British police team in Pakistan was also seeking to advance a separate investigation into the 2010 murder in north London of a senior MQM leader, Imran Farooq.
Three suspects in the case are being held in Pakistan. The UK police want to extradite one of the three - Mohsin Ali Syed - who they claim was present at the scene of the killing.
Pakistan is insisting that either all three should be extradited - or none at all.
The MQM denies any wrongdoing and insists that all the allegations made against it are false.
The British judiciary has been highly critical of the MQM. Back in 2011 a British judge adjudicating an asylum appeal case found that "the MQM has killed over 200 police officers who have stood up against them in Karachi".
During their investigation into the murder of Mr Farooq the police found £167,525.92 (about $235,000) in the MQM's offices in London and a further £289,785.32 in Mr Hussain's home in Edgware, north London.
Previous investigations in London uncovered a list in Mr Hussain's home itemising weapons, including mortars, grenades and bomb-making equipment. The list included prices for the weapons.
The Scotland Yard documents include a number of other British requests for assistance from their Pakistani counterparts.
The British asked for information about cash and weapons found at the MQM's Karachi headquarters. They also asked for official confirmation of Pakistani media reports that the MQM was involved in extortion in Karachi.