Barclays' Finance Director Chris Lucas has retired amid an ongoing investigation in the bank's activities by Britain's financial watchdog during the height of the global financial crisis.

Lucas will retire from the UK's second-biggest lender after six years as FD, Barclays said Sunday in a statement published on its website. Group general counsel Mark Harding has also stepped down, the bank said.

"Chris and Mark both expressed to me late last year that they were considering stepping down from their roles at Barclays," said CEO Antony Jenkins in the statement. "The rationale which each shared with me was consistent and, typically, grounded in wanting to do what is best for the bank. Their decision to retire was theirs alone."

Both will stay on in their roles until successors are found, the bank said.

Lucas was one of four current and former senior executives the bank said in a 27 July investor update were subject to an FSA investigation into the "sufficiency of disclosure in relation to fee payable under certain commercial agreements and whether these may have been related to Barclays Capital raisings in June and November of 2008."

On 20 August, the Serious Fraud Office said it had opended an investigation "into certain commercial arrangements between Barclays Bank and Qatar Holdings in 2008".

The Financial Times reported last week that the probe is focusing on whether Barclays lent the sovereign wealth fund money to buy its own shares during the height of the financial crisis.

Lucas departure comes one week after his name was mentioned in a court battle between Barclays and Guardian Care Homes, a British healthcare company that is suing the bank over a disputed interest rate contract.

The FD's name, along with 23 other current and former Barclays executives including former CEO Bob Diamond and current investment banking head Rich Ricci, were linked to the FSA's investigation into alleged libor manipulation that eventually led to the a bank's record £290m fine.

Last week Jenkins turned down a potential £2.75m bonus after saying it would be 'wrong' to receive extra compensation due to the number of mis-selling and market manipulation scandals that have rocked the bank.

"The year just past was clearly a very difficult one for Barclays and its stakeholders, with multiple issues of our own making besetting the bank. I think it only right that I bear an appropriate degree of accountability for those matters, and I have concluded that it would be wrong for me to receive a bonus for 2012 given those circumstances," he said.