BP is planning to announce the departure of chief executive Tony Hayward alongside its half-year financial results on Tuesday.

The BP boss will be replaced by Bob Dudley, who is currently overseeing the oil spill operation in the Gulf of Mexico.

The exit of Hayward, who has been vilified by American politicians since the 20 April blowout on the Deepwater Horizon rig, is the second dramatic change of leadership at BP in less than four years. Lord Browne, Hayward's predecessor, left the oil group after a spat with the then chairman, Peter Sutherland, and a sinking of the share price after the Texas City refinery fire.

Hayward, 52, is today locked in meetings with the rest of the BP board about the final details of his financial leaving package, but he is expected to go under basic contractual terms. That means a one year's £1m pay package but a giant pension pot of over £10m, capable of paying out more than half a million pounds a year from the formal retirement age of 60.

BP continues to insist that "Tony Hayward remains chief executive", and any change to this will be formally announced through the Stock Exchange.

The company had privately insisted that Hayward was working on a fightback to try to salvage his own reputation and that of a company that was once the largest on the London stock market.

But as the week drew on and a "new BP" strategy began to take shape, both Hayward and other board members began to realise that the US business and brand could only be salvaged under a change of guard.

Dudley is seen as the best candidate because he is a US citizen with a very strong track record at BP and previously at Amoco. He lost out on the position to Hayward but in recent months has been called on to give credibility to the Gulf clean-up operation. Dudley was best-known as chief executive of the Russian business TNK-BP, where he performed well until being forced to flee the country in what many observers saw as a Kremlin-inspired campaign to destabilise BP there and put it under more Russian control.