By law councils are allowed to obtain records of personal communications including phone calls and emails.

On two separate occasions last year, Doncaster Council applied for consent to access mobile and landline call records as part of criminal investigations.

Bosses made the information public following a request by the Free Press under the Freedom of Information Act, although they would not release further details about the enquiries, including whether they led to successful prosecutions.

Statistics nationally show surveillance is increasingly being used by councils in order to catch fly-tippers, benefit fraudsters and rogue traders.

But privacy groups say the move is another step towards Britain becoming a 'Big Brother' state and say the eight-year-old legislation is open to abuse.

A report by Sir Paul Kennedy, the Interception of Communications Commissioner, published earlier this year showed that 122 local authorities sought to obtain people's private communications in a nine month period in 2006.

Unlike police and intelligence services, councils cannot get the details of the content of calls or tap phones but they can ask for telephone subscriber and billing information when investigating or preventing a crime.

The records can help authorities confirm where a suspected criminal was at a given time.

A statement released by Doncaster Council said: "Doncaster Council does from time to time make enquiries regarding subscribers to both landline and mobile services as part of a criminal investigations.

"The council has applied to access mobile phones records on two occasions as part of criminal investigations in the year 2007. "

The authority's managing director Paul Hart added: "The council does not 'bug' telephone calls in any circumstances. There have been two occasions, when as part of an investigation into criminal activity, we have requested billing information only."

Independent councillor Martin Williams described the power exercised by the authority as "going a step too far".

He commented: "I am astonished that the council can do this - I didn't realise we had MI5 in the Council House! It's fair enough that our security services are engaged in surveillance but councils should be concentrating on providing good local services for local people, not snooping into phone and other records.

"I sit on the new Audit Committee and it is matters like this that should be on the agenda. I've never seen any reference to it in previous papers but members should be aware of what's going on."

Last November the council was embroiled in a row with some councillors over new IT policies that mean officers can check members' emails.

A number of councillors handed back authority-owned laptops because they could no longer guarantee privacy of messages from people they represent.