According to reports in the UK media, HMRC is targetting about 300 wealthy Britons who have used Liechtenstein foundations to hide income and assets from the tax man. About GBP300mn (USD599mn) in unpaid tax is supposedly at stake.

"We're dealing with very wealthy people who have used Liechtenstein's secrecy laws to escape UK tax regulations," an HMRC spokesman was quoted by the BBC as observing.

It is understood that HMRC has uncovered the identities of many of those account holders after it paid an informant in possession of data stolen from Liechtenstein's LGT Bank earlier this year. The tax department is believed to have paid GBP100,000 to the informant - a former employee of LGT - for the information.

The same informant also sold the information to the German intelligence service for about EUR4.5mn, sparking a huge tax evasion scandal involving hundreds of wealthy Germans.

HMRC's investigation into the Liechtenstein account holders is likely to form part of a wider probe into offshore bank accounts which began in 2007 with an amnesty designed to encourage account holders to declare assets with the carrot being a more lenient-than-usual penalty regime.

About 44,000 people took advantage of the offshore disclosure scheme, but in March 2008, HMRC began sending letters to thousands more taxpayers who did not respond to last year's inquiries, seeking further information on funds held in offshore bank accounts.

It is now thought that HMRC is ready to launch the next phase in its war against offshore tax evasion, and will soon begin to pursue criminal investigations against some 3,500 Britons lasting up to three years.