LONDON (Bloomberg) - Prime Minister Gordon Brown ordered the Treasury to take on people attempting to evade taxes overseas after the UK government joined Germany in investigating bank accounts in Liechtenstein.

The Treasury should "take whatever action is necessary" to combat tax avoidance, Mr. Brown's spokesman Michael Ellam told journalists in London yesterday.

German prosecutors are investigating 700 people suspected of sheltering income by placing funds in Liechtenstein. The UK said on Sunday it purchased a list of people suspected of holding accounts there, the latest in a series of efforts by the Labour government to allay concerns that the wealthy receive privileged tax treatment in Britain.

"We hope this marks the start of a wider campaign by the Treasury to ensure the super-rich pay their fair share," the Trades Union Congress, which represents seven million workers, said in a statement read by a spokesman.

Her Majesty's Revenue and Customs (HMRC), the arm of the Treasury that deals with tax collection, said that the investigation may uncover as much as £100 million ($196 million) in unpaid taxes. The department urged anyone who has hidden income or capital gains from the government to make "prompt and complete" disclosure or risk legal penalties.

"HMRC is determined to protect the UK's tax base from evasion, and in doing so we will use all the statutory powers we have," Dave Hartnett, chairman of HMRC, said in a statement. "It should now be clear to everyone that there is no safe hiding place for the proceeds of tax evasion."

Mr. Brown's government has toughened its efforts to protect tax revenue during the past two years and in October said it would bring the overseas earnings of wealthy foreigners inside the collection net for the first time. The Treasury also has said it will narrow a loophole on capital gains tax for entrepreneurs.

Chancellor of the Exchequer Alistair Darling on March 12 will set out changes to taxation for "non-domiciled" workers from overseas, giving them a choice of paying £30,000 annual levy or declaring their world-wide income. He also is tightening residency rules, bringing more people who live in the UK part time into taxation, and regulating trust investments offshore.

Plans for the new system have provoked protests from the banking and accounting industries, which say that many of the 115,000 non-domiciles who invest in Britain will leave for countries such as Switzerland or Singapore, hurting London's financial industry.

Mr. Brown has to balance the concerns of the financial industry, which provides £19 billion in export earnings and one million jobs in London, against protests from lawmakers and union leaders who say the rich have an unfair advantage.

The government "appears to be listening," Sir Ronald Cohen, founder of Apax Partners, said in an interview on Bloomberg Television. "I'm hopeful they'll come out" with proposals that will keep foreigners in the UK.

The gap between the rich and poor in the UK is too wide, according to 75 percent of the 1,003 people polled in an ICM Ltd. survey conducted earlier this month.

HM Revenue and Customs paid £100,000 for the data of 100 bank accounts held by Britons in Liechtenstein, an alpine country of 35,000 people that lies between Austria and Switzerland.

The move was made only after the German government paid as much as five million euros for a computer disc containing information on account holders.

"It's questionable morality," Kevin Phillips, a corporate tax partner at Baker Tilly in London said in an interview.

"If you're ruthlessly pragmatic to pay £100,000 to protect tax of £100 million, it's a good economic decision.

"If it were a criminal case and evidence were obtained in this way it would be inadmissible."