LONDON — Barclays Chief Executive Bob Diamond resigned Tuesday, the biggest departure in a financial markets scandal that has ripped through the bank’s senior management and sown the seeds for an investigation into Britain’s banking sector.

Jerry del Missier, chief operating officer, resigned hours after Diamond left and a day after the chairman announced he would step down. The bank released documents saying del Missier was responsible for ordering traders in 2008 to report dishonestly low borrowing rates because he had mistakenly concluded that the Bank of England had told Barclays to do so.

The Bank of England denies knowing of any impropriety in how British banks set their borrowing rates, but the question promises to dominate testimony that Diamond will give before a U.K. parliamentary committee today.

The executives’ resignations, effective immediately, came a day after Chairman Marcus Agius fell on his sword. Agius will leave the company only after a new chairman is found and will lead the search for a new chief executive. He will take on Diamond’s responsibilities until a new CEO is appointed.

Barclays’ management has come under fire since the bank was fined $453 million last week by U.S. and British regulators for submitting false reports on interbank borrowing rates from 2005 to 2009. Much of that activity originated from traders in Barclays Capital, the investment banking division that Diamond headed at the time.

“The external pressure placed on Barclays has reached a level that risks damaging the franchise – I cannot let that happen,” Diamond said Tuesday in the statement accompanying his resignation.

Britain’s Serious Fraud Office said Monday that it would decide within a month whether to pursue criminal charges in the case.

Barclays is one of a number of banks that regularly submit estimates of what it will cost them to borrow from other banks. These estimates feed into a calculation of the London interbank offered rate, known as LIBOR, which is used to determine payments from a range of financial contracts.

The London rate, and a related European interbank offered rate, are the benchmarks for over $500 trillion in global contracts, including loans and mortgages. Barclays has admitted submitting lower than actual figures on its interbank borrowing during the credit crisis in 2008.