Coast Mountain bus drivers are angry after finding hidden cameras secretly installed to monitor them on the job in many of the company's buses.

The company admits it installed the cameras in an effort to find the person responsible for vandalizing drivers' seats, but the union says it's a breach of trust.

Coast Mountain went public earlier this year when it mounted cameras in bus passenger compartments following a number of violent assaults against drivers.

But last week, a mechanic discovered a second camera aimed at drivers only and hidden inside the housing of camera used for regular surveillance.

"Every movement that [drivers] do would be watched," said Gavin Davies, of Canadian Auto Workers Local 111. "The biggest thing is the breach of privacy. This sends a clear message from this employer -- exactly how they feel about their employees. The mistrust is huge."

A total of 14 of the extra cameras were eventually found in buses operating in Richmond and Vancouver.

In February, about 60 drivers' seats were slashed, at a cost of about $400 each.

Seats were focus

The secret cameras were installed in June to try to zero in on the culprit, but drivers themselves weren't the precise target of the vandalism investigation, the company said.

"[The camera] wasn't focused on the operators, per se," Coast Mountain spokesman Stan Sierpina told CBC News. "It was focused on the seat."

"The investigation ended in August, but the company we used didn't take [the cameras] off like we asked them to," Sierpina said.

The day after the cameras were found, Coast Mountain President Haydn Acheson issued an internal bulletin.

"Surveillance is a last resort in any investigation and the company must exhaust all other avenues before initiating this kind of action," Acheson wrote.

The person responsible for vandalizing the drivers' seats has not been caught.

The union said it is seeking legal advice.