The shale gas and oil industry has expanded rapidly in the US, although controversy remains over fracking – releasing hydrocarbons by pumping water, chemicals and sand at high pressure to fracture the shale rock.

In his first appearance in front of a Parliamentary inquiry since RBS was part-nationalised, Johnny Cameron, former investment banking chief, said Mr Goodwin had a "frank exchange of views" over the issue with colleagues as the bank teetered on the brink of collapse in 2008.

But Mr Cameron, the only RBS executive to have faced action from regulators after being barred from senior roles by the Financial Services Authority, said it had a "moral culture" during Mr Goodwin's tenure.