Leicester City Council used controversial snooping laws to monitor the under-siege Bowstring Bridge site, the Mercury can reveal.

The authority said it applied to use a swivel and zoom function on an on-site CCTV camera to gather evidence after a council officer raised concerns over demolition workers' safety.

It was one of at least 22 covert investigations, or monitoring operations authorised by the authority in the past 12 months under the Regulation of Investigatory Powers Act (Ripa) – introduced in 2000 to oversee councils' use of surveillance.

The council said it used the powers at the Bowstring Bridge, in the city's West End, because of the risk of trespass, criminal damage and public disorder at the site.

Campaigners maintained a vigil near the bridge in the weeks leading up to the demolition.

The council said no-one was arrested as a result of anything caught on video.

The city council's director of environmental services, Adrian Russell, who signed off the application, said CCTV staff were told that it was only to be used for guarding against criminal damage and was not to be used to monitor protesters.

He said: "Strict guidelines must be met for an application under Ripa to be approved.

"It was made clear in the application that it was to be used solely to monitor instances of criminal damage, or trespass.

"We had no interest in filming protesters."

Fears over workers' safety at the site were fuelled by a series of attacks on fencing and gates, as well as allegations that some spiked objects had been thrown over boundary fences.

Applications under Ripa do not have to be signed off by an elected official.

Councillor Patrick Kitterick was cabinet member for regeneration in the run-up to the bridge's demolition. He said: "We were aware of generic threats to the works around the bridge.

"Some people e-mailed me saying they would disrupt work to the bridge and I informed police and council officers about that.

"However, I wasn't consulted on the use of these powers."

The city council's cabinet agreed, in August, to remove the bridge to make room for De Montfort University's planned swimming pool and sports centre.

The decision was unpopular with many people, who said it was an important part of the city's heritage.

The regulatory act applies to all local councils in England, every NHS trust and fire service, 139 prisons, the Environment Agency and Royal Mail.

The application for the CCTV camera was authorised on October 9.

It was cancelled on December 2, once demolition work was completed.