German supermarket chain Lidl intimidates, humiliates and bullies workers to maximise profits, according to a damning book released by a German union yesterday.

Services union Verdi presented its accusations, strenuously denied by the retailer, in the Lidl Black Book, published with a certain irony yesterday on International Human Rights' Day.

"Particularly noticeable at Lidl is the climate of fear stoked up by managers. Fear is, much more so than in other companies, a central instrument of personnel management [ at Lidl]," the book says.

A Lidl spokesman denied the main charges in the book, calling it a "defamation campaign", but did not rule out that individual managers mistreated employees.

The book's author, Mr Andreas Hamann, rejected this "bad apple" explanation.

"I kept hearing such stories over and over again during my research. It shows a pattern that runs right through all branches in the republic [ of Germany]," he said.

Lidl, second-largest German discounter, is owned by reclusive billionaire Mr Dieter Schwarz (65), and has more than 150,000 employees in 19 countries worldwide, including Ireland.

Mr Hamann's main attack is on the climate of fear, suspicion and insecurity he says reigns in Lidl supermarkets.

Employees' coats, bags and even cars are searched regularly, according to the book, with the burden of proof on employees that they bought and didn't steal any Lidl products found.

Employees are pressured to scan at least 40 items per minute and the performance pressure is so great that the authors say they found no employees able to take their full break entitlement.

Lidl said yesterday that staff would describe conditions "overwhelmingly positively".