BERLIN, Germany?Germany and Switzerland were on collision course on Monday over the Alpine state's cherished banking secrecy after Berlin said it might buy the names of suspected tax-dodgers from a whistle-blower.

Press reports said that a mystery informer had offered Berlin the names of between 1,300 and 1,500 people hiding money from the German tax authorities in Switzerland for 2.5 million euros ($3.5 million).

Switzerland warned Germany that buying stolen information "violates public policy and the principle of good faith...(and) constitutes a breach of the privacy of the clients concerned," refusing to cooperate if Berlin went ahead.

But with reports that the information would net Germany around 100 million euros in recovered taxes, German Chancellor Angela Merkel said "everything must be done to get hold of these data."

"Like every sensible person, I want to clamp down on tax evasion," Merkel told reporters in Berlin. "If these data are relevant we should aim to get hold of them."

She did not say, however, whether Germany might pay for the names.

The German finance ministry said that Berlin was considering following a 2008 "precedent" involving Liechtenstein, another Alpine country that has come under fire for helping investors conceal their wealth from the taxman.

In that case, the German secret service handed over five million euros for the names of hundreds of German business executives, sports stars, and entertainers allegedly hiding some four billion euros.

In the ensuing investigation, Germany clawed back some 180 million euros.

The scandal also claimed the scalp of Deutsche Post chief Klaus Zumwinkel, who got a two-year suspended jail sentence and was fined close to one million euros after admitting hiding money in the principality.

Germany handed other countries the names of some of their nationals and the scandal put tax havens in the international firing line just as the financial crisis sparked new calls for transparency in the banking industry.

Switzerland and Liechtenstein have since moved to clean up their acts, agreeing to share more tax information with other countries. As a result, both have since been removed from an OECD "grey list" of tax havens.

Swiss banking giant UBS last year agreed to hand over details of about 4,450 clients and United States taxpayers, although last month a Swiss court upheld an appeal by one taxpayer against the transfer.

Some in Germany, however, are cautious about paying for the information and with a new government in power after elections late last year, it is not clear that Berlin would cough up again.

Karl Heinz Daeke, head of the BDST German taxpayers' association, told NTV television that the government had to be "very careful" how it handled the situation.

Doubts emerged meanwhile about the identity of the whistle-blower.

The Financial Times Deutschland daily named him as Herve Falciani, an IT specialist formerly employed by British bank HSBC in Geneva, who passed on data to the French tax authorities.

"This is just a rumor," Falciani, 37, told AFP. "If they have any shred of proof, they should produce it."