Officials from HM Revenue & Customs (HMRC) are to probe up to 300 Liechtenstein accounts belonging to wealthy Brits.
The tiny country is said to be being used as a way for rich people to avoid paying taxes, with the HMRC expected to recover up to £300 million.
It is believed that the organisation was tipped off by a paid informant who was previously employed at the country's LGT Bank.
Liechtenstein's 15 other banks are increasingly coming under attack for not co-operating enough with foreign tax officials.
Speaking to the BBC, Paul Franklin, a spokesman for HMRC, said: "We're dealing with very wealthy people who have used Liechtenstein's secrecy laws to escape UK tax regulations."
Officials say the investigation into possible tax evasion could take up to three years to complete.
Located between Switzerland and Austria, Liechtenstein has a population of just 35,322 and, as well as being renowned as a tax haven, is popular with winter sports enthusiasts.


