Drivers are being warned to be on their guard against private car clamping firms after a rise in complaints about charges.

Stevenage town centre has been highlighted as an area of particular concern by Herts Trading Standards after it recorded an increase in complaints about the cost of being clamped on private land.

The watchdog said some motorists have had to pay up to �500 before their cars were released.

The practice is legal if prominent signs showing the penalty charge and company name are displayed, and clampers are licensed by the Security Industry Authority.

Town Centre Manager Tracey Parry said there should be much stricter controls about how much private clamping firms can charge.

She added: “Some businesses use them because if they don’t they don’t have any access for deliveries. It needs to work in the interest of businesses but should be fair and lawful.

“They adopt quite an agressive approach. They do charge an extortionate amount of money. They seem to make it up on the spot.

“It’s not something as a town centre partnership I want - people to be unjustifiably clamped.”

Richard Thake, Herts County Council cabinet member for community safety, said companies are entitled to charge motorists a reasonable release fee but warned drivers to check for signs and not risk a five-minute stay.

He added: “While we cannot stop these companies if they are operating legally, we would like to urge motorists to be extra careful when parking in areas they are unfamiliar with. Check the area for signs informing you if clamping is in operation and stick to the conditions that allow parking in the area.”

If you think you have been unjustifiably clamped or unfairly charged, contact the Citizens Advice consumer service at www.direct.gov.uk/consumer or call 08454 040506.