The U.K. Financial Conduct Authority asked lenders and otherfinancial services firms to complete until April 15 initial investigations intowhether they are linked to Panama-based law firm , the Financial Times reported April 7, citinga letter from the FCA.

The regulator asked financial institutions to detail whataction they are taking in the wake of the Panama Papers leak. "Beyond 15 Aprilwe will require updates on any significant issues or relationships identifiedand a full response, detailing your findings, when your investigation isconcluded," the FCA wrote in an April 4 letter, according to the FT.

Additionally, the FCA pointed out to the letter's recipientsthat U.K.-based entities' offshore branches and units outside Europe arerequired to meet British standards of monitoring customer accounts and ofknowing their clients.

The regulator confirmed sending the letter to about 20 companiesin the week of April 4, the report added.