LONDON, April 7 (Reuters) - Britain's Financial Conduct Authority has asked 20 banks and other financial firms to check if they have any ties to Panama law firm Mossack Fonseca, the regulator said on Thursday.
A massive leak of documents from the firm released this week detailed how the world's rich skipped through loopholes to park cash in low-tax jurisdictions.
"We have written to the firms earlier this week," an FCA spokeswoman said.
Recipients of the letter have been given until April 15 to respond to the disclosure request.
More than 500 banks, their subsidiaries and branches registered nearly 15,600 shell companies with Mossack Fonseca, according to the International Consortium of Investigative Journalists (ICIJ). HSBC, Britain's biggest bank, and its affiliates created more than 2,300 in total, the ICIJ says.
HSBC has dismissed suggestions it actively used offshore structures to help clients cheat on their taxes.
The bank has said the documents from Panama pre-dated a thorough reform of its business model.
Spokespeople for HSBC and Barclays declined to comment on the FCA correspondence.
RBS and Standard Chartered both said they were reviewing their operations and co-operating fully with regulators on the issue.
News of the FCA's letter follows calls from Conservative lawmaker and chairman of Britain's Treasury Select Committee, Andrew Tyrie, for a thorough investigation of the trove and prosecutions "wherever possible".
"The government's, and HMRC's (Her Majesty's Revenue and Customs), objectives - to collect the correct amount of tax and clamp down on illegality - require a great deal of transparency. The government will need to press for more," Tyrie said on Wednesday. (Reporting by Huw Jones, Sinead Cruise, Lawrence White and Andrew MacAskill; Editing by Jason Neely and Susan Fenton)