”To watch over people this way in order to catch a perpetrator seems very much like the secret surveillance that only the police and other crime-fighting agencies can undertake, and then only in the case of serious offences,” said director general Göran Gräslund in a statement on Tuesday.

The Data Inspection Board had received complaints that SJ had been monitoring cleaners by use of secret cameras without informing the staff that they were being filmed.

According to SJ, they had been suffering from problems with pilfering on their trains.

The company had noticed significant shrinkage in the stocks of liquor, beer, food, and candy found on several restaurant cars, the Metro newspaper reported at the time.

To combat the problem, the company installed secret surveillance cameras on two of the trains were most of the offences seemed to occur.

Following the camera’s installation, ten members of the train’s cleaning crews were caught in the act, with one suspect being recorded literally wiping the shelves clean and depositing the booty into a large plastic garbage bag.

However, union representatives complained that SJ lacked a permit to install hidden surveillance cameras in the workplace.

And according to the Data Inspection Board, SJ was violating current Swedish legislation on camera surveillance when they had the cameras installed.

In their decision, the agency noted that secret surveillance is only allowed in extenuating circumstances, when the aim is to combat serious crime.

Pilfering was not deemed serious enough to warrant hidden cameras.

Earlier in the year the Data Inspection Board approved hidden camera surveillance at Danderyds Sjukhus in Stockholm, which had been experiencing problems with sabotage of sterile goods.

”But that was exceptional circumstances due to the serious risks that the sabotage could ensue,” Gräslund said.