Barclays chairman quits after devastating Libor blow LONDON (Reuters) - Barclays Plc Chairman Marcus Agius quit on Monday, saying an interest rate rigging scandal had dealt "a devastating blow" to the bank's reputation and "the buck stops with me." Agius, chairman at Barclays for 5-1/2 years, will stay in his position until a succession plan is in place. The move may be seen as an attempt to take the heat off Chief Executive Bob Diamond, who along with Agius has faced calls to resign after the bank was last week fined $453 million by British and U.S. regulators for submitting inaccurate submissions on the Libor interest rate. "Last week's events - evidencing as they do unacceptable standards of behavior within the bank - have dealt a devastating blow to Barclays reputation ... the buck stops with me and I must acknowledge responsibility by standing aside," he said in a statement. Barclays has admitted that some of its traders attempted to manipulate the setting of the London interbank offered rate (Libor), which is used worldwide as a benchmark for setting prices on about $350 trillion of derivatives and other financial products. The scandal threatens to draw in more banks and potentially regulators and authorities. "I am truly sorry that our customers, clients, employees and shareholders have been let down," Agius said. The bank said it would launch an audit of its business practices, led by Michael Rake, its senior independent director who will move up to deputy chairman. The audit will undertake "a root and branch review of all of the past practices that have been revealed as flawed" and assess implications for its practices and culture. Reporting by Steve Slater; editing by Anna Willard