"According to what we know, this is the case," Chief Executive Boris Collardi told the SonntagsZeitung. "As part of our stepped-up controls and a thorough internal investigation we recently discovered a case of data misuse and were able to identify the alleged thief."

Switzerland and Germany have been locked in a dispute over tax cheats for years, with officials in Germany repeatedly paying for stolen bank account data, to the anger of their Swiss counterparts.

The two countries have signed an agreement to end the dispute and impose a retroactive levy on undeclared funds while preserving secrecy. Yet the agreement must still clear Germany's parliament, where the opposition Social Democrats (SPD) say it is too lax on tax cheats.

According to the SonntagsZeitung, the stolen data on clients found its way into the hands of tax investigators in the German state of North Rhine Westphalia, with the thief paid an undisclosed sum.

The suspect, a bank employee working in Zurich, acted alone and has been arrested, the paper said.

Last year, Julius Baer agreed to pay German tax authorities 50 million euros to close a tax probe. Germany has promised to stop buying leaked bank data naming suspected tax cheats if the tax deal comes into force.

M&A PAUSE

Baer announced on August 13 that it planned to buy the overseas wealth management business of Bank of America Merrill Lynch (BAC.N).

Baer, whose profit has come under pressure due to the tax disputes, is keen to expand abroad, and acquisition of the loss-making unit means that about half of all the Swiss bank's clients will be in faster-growing emerging markets - chiefly Asia but also Latin America and the Middle East.

Collardi told the SonntagsZeitung that no further acquisitions were planned for now.

"We don't have the management capacity to do a second buy at the same time," he said. "In a year we can think about a new acquisition again."

Collardi said he intended to turn the new unit around by raising earnings and lowering costs, including by cutting jobs and combining two offices in Singapore.

"We expect (to cut) several hundred jobs, including in Switzerland," he said.

(Reporting by Catherine Bosley; Editing by Helen Massy-Beresford)

• A Permanent Economic Emergency