Up to 40 people have been put under surveillance by Glasgow City Council, figures show.

The authority was exercising its powers under the Regulation Of Investigatory Powers Act, which allows undercover staff and private investigators to target people they believe have been acting unlawfully.

Those suspected of committing health and safety, food safety, trading standards and environmental protection offences have prompted investigations.

People thought to be operating illegal money lending schemes, selling faulty goods, contaminated food or those suspected of housing benefit fraud can also find themselves under surveillance.

Covert tactics can also be used to collect information about suspected anti-social neighbours, overcrowded licensed premises and fly tippers.

The undercover staff use video cameras to covertly film people and places where they suspect scammers, such as illegal loan sharks, are operating.

Council officers have also obtained information about suspects' telephone subscriptions.

Guidelines state the investigation subjects must be unaware of the operations and undercover officers can recruit private investigators and informants.

While investigators cannot intrude into homes and cars, they can watch them from outside.

And council guidelines say that information or evidence can be collected on devices carried into homes by "covert human intelligence sources" if they are invited in.

Figures released under Freedom Of Information laws, show that in 2012 the chief executive of Glasgow City Council authorised 20 such covert operations.

Of these, six direct surveillance operations took place in the city and in 14 cases council officers obtained information about peoples' phone subscriptions and service use.

In 2011, five direct surveillance operations were authorised and 15 suspects' telecommunications information was accessed.

Test purchases of suspected faulty or counterfeit goods, unannounced site visits, and the use of children in stings to detect underage sales can be used without such special authorisation.

Glasgow City Council said it could not provide information about the individual cases. It said this would jeopardise the "prevention and detection of crime".

A spokeswoman said: "Glasgow City Council takes proportionate and appropriate use of these powers very seriously and, as a rule, only authorises their use in tackling genuine offences where there is a realistic chance of prosecution.

"We use them in investigating benefit fraud and powers have also been used by the Scottish Illegal Money Lending Unit, which the council operates on behalf of national government.

"Without the Regulation Of Investigatory Powers (Scotland) Act, the work of that team, targeting loan sharks and identifying and supporting their victims, would effectively become impossible.

"Our Trading Standards Unit has also made use of the Act's powers in securing convictions against counterfeiting gangs and consumer scams.

"Other cases have involved environmental crime, including fly-tipping."

linzi.watson@ eveningtimes.co.uk