The Times reports that a total of 20,919 contractors, including IT professionals and NHS locums, have told HMRC that their true earnings were disguised for years in avoidance schemes.

The freelance workers allowed their financial affairs to be managed by offshore-based umbrella schemes, which collected their wages on their behalf and then paid them in “non-repayable loans” that hid their NI and income tax liabilities.

The freelancers who have so far admitted taking part in the schemes are believed to owe HMRC an average of £50,000 each in underpaid tax, meaning they will have to collectively repay about £1bn.