Motorists have been given advice from consumer focus groups on using car parks run by private firms.
Citizens Advice, Consumer Focus and the Trading Standards Institute say that private firms are being overzealous in issuing parking fines.
Consumer Focus estimates that this year alone motorists were hit with between £38 million and £58 million in disputable parking charges.
Citizens Advice, which dealt with complaints from consumers who were disputing their fines, said common reasons for parking tickets being issued were broken ticket machines and poor signage.
The consumer groups are calling on the Government to create an independent complaints procedure for aggrieved motorists, and have warned motorists to be vigilant when using car parks run by private firms.
Citizens Advice chief executive Gillian Guy said: "We're worried that unscrupulous private car parks will go ticket crazy as they look to make a buck from busy shoppers - issuing tickets with little or no grounds to do so."
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