MANCHESTER'S ''gridlock-city'' reputation is being aggravated by faulty car park signs which are giving motorists false information.

The illuminated boards are declaring parks ''FULL'' even though hundreds of spaces are still available, a Manchester Evening News survey revealed.

With the city centre bursting at the seams and the Christmas shopping rush worsening the bottlenecks and congestion, car park bosses are being urged to act quickly.

The Manchester Evening News carried out an independent investigation which revealed startling differences between what was displayed on the signs and what was actually happening in the car parks.

In the worst case, we found the top three levels of one of the city's main multi-storey car parks contained only five cars despite signs showing all spaces were full.

The sign in Newton Street for Chorlton Street car park was displaying full but inside, there were more than 350 free places, including almost all of the top two floors.

At the weekend, Gartside Street car park was displayed as full but, in fact, there were 72 spaces available. The High Street car park which serves the Arndale Centre was also said to be full but there were 32 spaces on lower floors and only four cars parked on levels 12, 13, and 14, leaving dozens of free spaces.

Church Street car park was said to have 109 spaces whereas, in fact, there were only 31. Two signs for the Palace car park in Whitworth Street, one in Whitworth Street itself and one in nearby Oxford Road, were not illuminated at all.

The AA said with Christmas approaching it was vital every available car park space in the city centre was flagged up.

A spokesman for the RAC said ''They have got to get the problem sorted quickly. If it continues then people are going to turn around and go to the Trafford Centre instead.''

Angie Robinson, chief executive of Manchester Chamber of Commerce and Industry, said: ''A lot of work is being done in Manchester to attract more people into the city. If the electronic boards are giving out false information, then it's bad news for traders and retailers.''

National Car Carks, who operate the city's car parks in conjunction with Manchester city council, say they are aware of the problem and are taking steps to sort it out.

According to the company, the signs are fed data automatically every 15 minutes from the car park turnstiles and they believe this delay could account for the errors.

But car park controllers at Manchester city council say there are good reasons why the readouts don't tally with reality.

They say the car parks register full when there are still a handful of spaces left so that people don't end up driving around and around the car parks looking for an elusive spot. And they claim spaces that are empty often register as being taken because they are part of a block contract booking.

But frustrated driver Peter Campbell said: ''Contract bookings aren't going to be on the top foor and even if they were they can't account for 200 spaces.''