Paul Skinner is to step down as chairman of Rio Tinto, the Anglo-Australian miner, amid speculation that he will move to head the board at BP this year.

His replacement at Rio will be Jim Leng, the chairman of Corus, the steelmaker, since 2003.

Mr Leng, 63, will join Rio as the company grapples with big debts and falling metal prices. It has been outlining measures to cut capital expenditure this year from $9 billion (£6.1 billion) to $4 billion.

It is also likely to reveal a big drop in fourth-quarter production today.

Mr Skinner, 64, had been widely expected to announce his retirement from Rio at its annual meeting in April, having seen off a £70 billion hostile bid from BHP Billiton.

He is understood to have been lined up to replace Peter Sutherland, the chairman of BP, the oil group.

Formal confirmation of this appointment is likely to be made after Rio announces its full-year results in the first week of February.

Mr Sutherland has been the chairman of BP since 1997 and he clashed two years ago with Lord Browne of Madingley, who was chief executive at the time.

Lord Browne wanted to remain at the oil giant after his 60th birthday, but Mr Sutherland believed new blood was needed.

Lord Browne eventually stepped down and was replaced by Tony Hayward last year. Mr Sutherland’s retirement will mean that the top two jobs in the UK’s largest company have changed within 12 months.

Mr Skinner has experience of mentoring a new, young chief executive after the appointment of Tom Albanese at Rio in 2007.

Moreover, Mr Skinner would appear to be an obvious choice to lead BP, as he worked in the oil industry before moving to his non-executive role at Rio.

However, he leaves Rio, after six years, in a fragile state. Its share price has fallen from £71.67 a year ago to £13.80 yesterday as metal prices have collapsed.

Mr Skinner also played a big role in the acquisition of Alcan, the Canadian aluminium producer.

Rio took on $40 billion of debt to buy Alcan and is struggling to meet repayments.

The company had promised to sell $10 billion of assets by the end of 2008 as part of its repayment plan but could not because of the credit crunch.

Rio plans to continue selling assets but also wants to cut capital expenditure and 14,000 jobs.

There was speculation that Rio might be forced into a rights issue, which helped to push the share price down by nearly 12 per cent.

During his tenure, Mr Skinner was instrumental in leading resistance to a takeover approach from BHP.

Mr Skinner insisted that the deal did not value Rio’s assets highly enough, but analysts have questioned whether his refusal to accept it has cost Rio investors, given the collapse in the shares over the past couple of months.

Mr Skinner said: “After the termination of the BHP Billiton pre-conditional offers for the group and the identification of a well-qualified successor, now is a good time for me to announce my decision to stand down.”

BP said that it was still to make a final decision on a new chairman.

Mr Leng has his own experience dealing with takeover offers. He was chairman of Corus, the former British Steel, when it was approached by Tata, of India, two years ago.

Corus eventually accepted a £6.7 billion offer and Mr Leng became deputy chairman of Tata Steel.

He is also a non-executive director of Pilkington, the glassmaker.

Previously he was the chief executive of Laporte, a speciality chemicals producer, and a managing director at John Waddington, the company behind games such as Cluedo and Monopoly in the UK.

Mr Leng said: “Rio Tinto has a superb set of assets and strong prospects. I look forward to working closely with chief executive Tom Albanese and his team as we steer the company through the challenges of the current economic climate and beyond.”

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