Tax authorities in Britain have started investigations into some of the hundred people named by a whistleblower as having accounts in Liechtenstein, and are aiming to collect more than £200 million in unpaid taxes and fines.

HM Revenue & Customs estimates that it is owed £100 million in backdated tax from the account-holders named in a DVD it bought from an informant several weeks ago.

The Revenue has yet to contact some of the names on the list, but it is estimated that they could have placed as much as £5 billion in accounts in the principality.

Those who are found to have evaded tax on their offshore assets will have to pay the tax plus interest. In addition, they will face fines of up to 100 per cent of the tax owed.

The Revenue’s inquiries could also lead to criminal prosecutions. The maximum penalty for tax evasion is seven years in prison. It is understood that the Revenue is also looking at the possibility that money laundering was used to get some of the the money into the offshore accounts.

The Revenue stood by its decision to pay the informant up to £100,000 for the list of names, which is understood to have been stolen from LGT, the biggest bank in Liechtenstein.

A spokesman said: “The real theft is from UK taxpayers. The material has become available and we need to make sure that UK law is kept.”

Vince Cable, deputy leader of the Liberal Democrats, said: “Paying informants is always ethically questionable, but in this case it was warranted.”

Legal experts said that the taxman regularly pays whistleblowers for tip-offs that lead to the collection of tax and that information would be admissible in court. However, Roger Bindschedler, a tax partner at Howard Kennedy, a firm of solicitors, said that the Revenue would probably use the stolen data as a springboard for further, more conventional research.

Anyone hoping to use data protection laws to have stolen evidence struck out or seeking a court injunction preventing the Revenue from using the data is likely to be frustrated. Sarah Needham at the solicitors’ firm Macfarlanes said: “The Data Protection Act contains exemptions for information obtained in the course of preventing crime or collecting taxes.”

The Revenue has been aggressively pursuing those using offshore accounts to avoid paying tax. Last year it contacted five high-street banks for details of all customers with offshore accounts, although it gave account holders the opportunity to come forward and escape full penalties. Nearly 65,000 people did so, netting the Revenue £400 million. Those who did not come forward are likely to be investigated. The Revenue is asking for details of offshore accounts from the other 150 UK financial institutions.

It is estimated that there is a total of $3,000 billion (£1,500 billion) in global assets held in offshore accounts. These accounts are available to people with as little as €25,000 (£19,000). The average customer has between €2 million and €3 million of investable assets.

Liechtenstein is one of only a handful of tax havens which has refused to share information with tax authorities in other European countries in line with an EU directive of several years ago. As a result it, along with seven other countries including Monaco and San Marino, must pay a 15 per cent levy on the total savings held in their banks, rising to 35 per cent by 2012.

Experts said that sophisticated investors were usually drawn to Swiss offshore accounts. One said: “Liechtenstein offers a more boutique-style service, with the options tending not to be as sophisticated as in Switzerland.”

Investigators in Germany have been visiting hundreds of addresses in the past week after the same informant handed over 1,000 names. Klaus Zumwinkel, chief executive of the state-run postal service Deutsche Post, stepped down earlier this month amid claims that he evaded €1 million in tax by using a Liechtenstein account.

It is understood that the tax authorities in the United States have also acquired files, and have been using them to recoup lost tax revenue.