(Reuters) - Britain's top bank regulator and a former executive in the middle of an interest rate scandal at Barclays face a grilling by British lawmakers on Monday over what they knew about an affair that has drawn in banks, regulators and politicians on both sides of the Atlantic.

The House of Commons Treasury Select Committee will question Jerry del Missier two weeks after he quit as chief operating officer of Barclays, the British bank hit by an interest rate manipulation scandal that has blown up into a political storm. He w as the trusted investment banking lieutenant of Bob Diamond, the Barclays chief executive who quit the same day.

Del Missier is said by Barclays to have misinterpreted a message from Diamond and told the bank's staff that the Bank of England had sanctioned them submitting lower rates to massage down the London Interbank Offered Rate, or Libor, the rate that underpins global transaction worth trillions of dollars.

Del Missier has yet to comment publicly on the matter and his evidence could shine a light on who knew what at Barclays after testimony from Diamond which some committee members have characterised as misleading, a charge Diamond has rejected.

Adair Turner, chairman of the Financial Services Authority (FSA), will follow del Missier before the committee. He will face questions on the regulator's involvement and whether it was tough enough when rate rigging occurred between 2005 and 2009.

Barclays was fined a record $450 million last month by U.S. and British authorities for manipulating the Libor interest rate. Barclays will pull out of the rate-setting panel for interbank lending in the United Arab Emirates because of its involvement in the Libor scandal in Britain, industry sources told Reuters on Sunday.