Britain’s richest man, Sir Jim Ratcliffe, who was knighted less than a year ago for his services to business and investment, has been planning to avoid up to £4bn in tax after switching his home and his fortune to Monaco.

The Sunday Times can disclose that the prominent Brexiteer, who built up the chemicals giant Ineos, has been working with the accountant PwC on the tax avoidance plan. This would see him and senior executives Andy Currie and John Reece legally share between £1bn and £10bn tax-free, depriving the Treasury of between £400m and £4bn.

A source with knowledge of the plan described the upper end of the range as “egregious” and said it involved “labyrinthine” structuring. Another source said the plan had not yet