LONDON, July 3 (Reuters) — Barclays Plc Chief Executive Bob Diamond quit with immediate effect on Tuesday over an interest rate-rigging scandal, becoming the highest-profile victim so far in a probe that spans a dozen major banks across the world.

Britain’s third-largest bank said that outgoing chairman Marcus Agius — who himself announced his departure a day earlier - would lead the search for a new executive.

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

Agius announced his resignation on Monday in the scandal over traders manipulating the London Interbank Offered Rate (Libor), which is used worldwide as a benchmark for prices on about $350 trillion of financial products.

But Agius said he would stay in office as long as the search for a new chairman continued.

Barclays was fined $453 million by US and British authorities, becoming the first bank to settle in an investigation that is looking at more than a dozen others, including Citigroup, UBS and RBS.

British finance minister George Osborne welcomed the resignation.

“I think it’s the right decision for Barclays, I think it’s the right decision for the country because we need Barclays bank focused on lending to our economy and not distracted by this argument about who should be in charge,” Osborne told BBC Radio.

“I hope it’s a first step to a new culture of responsibility in British banking.”