The British tax authorities have paid an informant for the bank details of scores of wealthy Britons. The records were stolen from one of the world’s most secretive tax havens.

HM Revenue & Customs paid £100,000 for data that it is using to launch investigations of up to 100 British citizens who have accounts at Liechtenstein’s biggest bank.

British authorities regard it as a coup to have penetrated accounts that have been beyond their reach for decades. “There will be many frightened people who thought Liechtenstein was secure,” said a City accountant.

Anyone found to have evaded tax faces fines of up to 100% of the money owed to the Revenue and, where deliberate deception is proved, a jail sentence of up to seven years.

The bank informant has already provoked a storm in Germany by selling data on 750 wealthy Germans’ accounts to the country’s intelligence service for £3.2m in January last year.

Homes and offices of dozens of suspected tax evaders in Germany have since been raided.

The suspected whistleblower, accused of stealing data from the bank, was sacked and convicted of fraud. He also offered data to tax authorities in America, Canada, Australia and France.