Peter Schaar, the federal data protection commissioner, regards the practice as unconstitutional.

Berlin -- Frau P could be having an affair with Herr R and those tattoos on the forearms of Frau N could indicate a previous spell in prison.

Detectives employed by large German discount chain Lidl have collected information of this kind on employees, using tiny cameras and voice recorders to monitor their behavior while dealing with customers at the till, stacking the shelves or on their way to the lavatory.

Peter Schaar, the federal data protection commissioner, regards the practice as unconstitutional.

"I assume that the relevant data protection agency will become involved and launch a probe, if this kind of practice has come to light," he told the weekly Stern, the magazine that uncovered the spying.

An Interior Ministry spokeswoman in the state of Baden-Wuerttemberg confirmed that an investigation was underway.

But discounter Lidl denied that spying on its employees was a company-wide practice, insisting that it was confined to specific outlets where theft was suspected.

"We're trying to find out where goods are disappearing," board member Juergen Kisseberth told commercial news broadcaster n-tv. Lidl's German branches suffered stock losses of 8 per cent last year, he said.

The broadcaster showed piles of documentation on Lidl workers, citing remarks taken from the reports, such as "Frau P and Herr R have a very familiar relationship."

The performance of staff was also evaluated, with remarks like "introverted and naive presentation" being noted down by the electronic snoops.

"Her circle of friends consists largely of drug addicts," was one recorded observation. Notes were made on staff sitting chatting during their breaks and complaining about pay and service conditions.

The Verdi services trade union said the surveillance was clearly unconstitutional.

Verdi retail representative in Baden-Wuerttemberg Bernhard Franke told DPA that the allegations, if true, fitted "the system of permanent control and repression in the company."

Verdi charges Lidl with intimidating its lowly paid staff. Franke noted that the workers' councils provided for under German labor law and common in most larger companies were virtually absent at the discounter.

Founded in Germany in the 1930s, Lidl now has more than 7,000 outlets across Europe, selling mainly food and household products. It employs around 80,000 staff, most of them on low wages.

Verdi and other trade unionists have regularly criticized the company's labor practices as ruthless, charging that staff are paid only for the hours the outlets are actually open and not for preparing beforehand and cleaning up after hours.

Lidl has also hampered union activity by threatening to close outlets where staff have shown signs of organizing, Verdi says.

Verdi retail spokesman Achim Neumann said he had grown accustomed to Lidl's labour practices over the years, but that even he had been surprised by the snooping.

"This provides a totally new dimension to the company's practices," he said.

DPA with Expatica