A worldwide crackdown on avoidance and evasion by the wealthy was launched on Friday by more than 30 countries, which promised a joint pursuit of individuals hiding money offshore.

Describing some rich individuals as posing “a major risk” to revenue bodies, the tax authorities said that greater opportunities for aggressive tax planning were available to the wealthy. In a report published on Friday, they cited estimates that 70 per cent of the 500,000-odd Britons in the very wealthy bracket received advice from a financial expert.