The decision follows a number of complaints last month from customers of a "well-known fast-food chain" which had cameras in the toilets of one of its outlets.

"There is no justification for a company installing CCTV cameras in its public toilets unless it was to remedy problems which had previously occurred on a frequent, as distinct from an isolated, basis, " said Tony Delaney, assistant data commissioner in charge of investigations.

However, in the fast-food chain under investigation, the data commissioner decided the company was justified in putting cameras into its toilets as "very serious incidents had occurred in the toilets of the restaurant, requiring the presence of the emergency services".

Delaney said, "We investigated other outlets of the fast-food chain and found no cameras in the toilets so no action was taken."

He stressed that while CCTV cameras are legal, their use is controlled by the data protection acts.

Businesses should inform staff and the public of the presence of cameras, otherwise they could be in breach of the act, warned Delaney. He said, "If monitoring of customers is necessary for security purposes then the business would need to have strong grounds for installing CCTV in a toilet area."

Some years ago a large supermarket chain was forced to pay out thousands of euro in compensation to its female staff after they discovered cameras hidden in the ceiling of the women's toilets. The supermarket said they were installed to stop staff pilfering.

Barry Walsh of A & L Goodbody solicitors who specialises in employment law said the use of CCTV in workplaces is a "very grey area" and warned that employers should be cautious on their use. "Specific legislation on the use of CCTV would be helpful, " Walsh said.