Scott will be appointed chairman of a new risk committee at the bank, which will see RBS strengthen its capital position and prepare for the Government’s insurance scheme for toxic assets.
Former Coca Cola head of UK and Ireland Penny Hughes will also join the revamped board.
Standard Life chief executive Sandy Crombie became a non-executive director in May.
RBS is currently 70 per cent state-owned after receiving a £20bn taxpayer-funded bail-out last year.
Scott revealed earlier this year he was stepping down from his role at Aviva. He has been with the insurer for 36 years.