Barclays chairman Marcus Agius poised for departure

Agius expected to leave his post shortly following the bank's £290m fine for its role in attempts to rig interest rates

Marcus Agius, chairman of Barclays. Photograph: Micha Theiner/City AM / Rex Feat

Marcus Agius, the chairman of Barclays, is poised to step down after political calls for a top-level departure from the embattled bank.

Sir Michael Rake, a former top accountant and senior independent director on the board of the bank, is regarded as the most likely candidate to be temporarily installed as chairman while a full-time successor is found.

The frenzied speculation about a boardroom shakeup at Barclays is taking place as the chief executive, Bob Diamond, and Agius prepare to be questioned by MPs on the Treasury select committee this week. Efforts are gathering pace to establish what the board knew about attempts to rig interest rates that landed the bank with a record £290m fine last week.

The exact timing of Agius's departure is unclear but it is likely to take place in the coming days, possibly on Sunday night.

The fine, and embarrassing emails disclosing the way that traders attempted to manipulate the interest rates, unleashed a wave of political fury which will intensify this week when MPs hold their hearings on Wednesday and Thursday.

Agius has had a frosty relationship with shareholders for much of his tenure. On Saturday the bank insisted he had no plans to leave.

In 2008 the bank turned to Middle Eastern investors to raise capital in a move that infuriated UK investors as it reduced their influence in the company by ignoring the principle of pre-emption.

Agius also came in for criticism following the revolt over Diamond's £17m pay at the annual meeting in May. That has left him vulnerable to further criticism in the light of the revelations about attempts to fix interest rates known as the London interbank offered rate (Libor) and the European equivalent, Euribor. These are two benchmarks that are the basis for pricing an array of financial products, potentially affecting the price at which households and businesses borrow money.

From 2005 the Barclays traders are said to have tried to alter rates to help themselves and rival traders, while in 2008 – when Barclays raised concerns about Libor – the bank is said to have kept rates lower because higher rates might have indicated it was in financial difficulty. At one point, the so-called submitters are said to have believed they were operating under the instruction of the Bank of England.

Despite the political clamour, which is focusing on Diamond, the board is thought to believe that its response to the scandal has been sufficient.

Diamond has forfeited his bonus for 2012, as have his close colleagues Jerry del Missier and Rich Ricci as well as the finance director, Chris Lucas.

Shareholders, though, want to claw back bonuses from prior years and are concerned about the impact of political intervention, which has already contributed to a £4bn slump in the company's value in just 72 hours.

Some shareholders are letting it be known that the departure of the chairman in the short term might be more acceptable to them, as there is no obvious successor to Diamond.