Uproar as Germany pays €2.5m for stolen Credit Suisse data

Files are set to expose 1,500 tax evaders – and intensify threat to traditional Swiss banking secrecy

Germany's government has unleashed a legal, political and diplomatic storm by paying an estimated €2.5m (£2.2m) for a CD of German depositors' data illegally taken from Credit Suisse's Zurich offices.

The CD's files indicate tax evasion by some 1,500 individuals amounting to €400m, the largest single case in modern German history. Estimates suggest 100,000 Germans have untaxed deposits of over €30bn in Swiss banks.

Andres Luther, a spokesman for Credit Suisse, insisted: "We have as yet no concrete indication that this data is sourced from us."

Credit Suisse documents quoted by the Süddeutsche Zeitung show that the bank, from 2004, wished to find more legal German clients because Germany had "made it more difficult to produce untaxed funds". Aggressive tax authorities and tough anti-terrorist laws, plus clients' willingness to spend rather than save, led to the changed strategy and the search for taxed deposits.

However, the CD – called by the newspaper "the top-earning CD ever" – contains a mass of historic and recent transaction data, and a picture emerges of rich Germans hiding untaxed fortunes in Switzerland over decades. Credit Suisse insisted last week that it has "neither the ability nor the duty to know its clients' tax position". But its internal documents showed tax-evading clients were advantageous as they require no marketing or advice. Contact with the bank was avoided rather than sought.

Tax evaders with Credit Suisse bank accounts face a tough choice. If their data is on the CD, they could face up to 10 years in jail unless they report their offence to the authorities.

The German Finance Minister, Wolfgang Schäuble, encouraged evaders to confess and defended the CD purchase because similar data was acquired from Liechtenstein by the German secret services and accepted as evidence by the courts. This resulted in the disgrace last year of the former chairman of Deutsche Post, Klaus Zumwinkel, who was given a two-year suspended sentence and ordered to pay a €1m fine for tax evasion. Legal authorities think he escaped lightly. The Liechtenstein data resulted in 200 German court cases.