July 4 (Reuters) - Britain's 'bad bank', which is charged with winding down the assets of two bailed-out lenders, repaid 3.3 billion pounds ($4.27 billion) to the government last year.

UK Asset Resolution (UKAR), a state-run loan firm that does not take on new business, said it has now returned 23.7 billion pounds to the government, almost half the total value it owed when it was created in October 2010.

UKAR is winding down the loans of Northern Rock and Bradford & Bingley, two of Britain's customer-owned building societies which were nationalized in the run-up to the 2008 financial crisis.

UKAR's underlying profit before tax fell by almost 33 percent to 706 million pounds in the year ended March, reflecting in part a 9 billion pound reduction in its loan book.

UKAR sold a portfolio of mortgages issued by failed lender Bradford & Bingley for 11.8 billion pounds to insurer Prudential and buyout firm Blackstone in March in one of the biggest deals of its kind.

Sky News reported last week that Blackstone was now looking to buy 6 billion pounds of Bradford & Bingley mortgage loans.

UKAR did not provide any details of possible sales in its statement. ($1 = 0.7727 pounds) (Reporting by Noor Zainab Hussain in Bengaluru; Editing by Rachel Armstrong)