Only 800 sites out of a possible 10,000 car parks have joined the scheme, although participating sites have seen a 70 per cent reduction in crime.
Fleet vehicles, carrying expensive tools and sales samples, have the most to lose to thieves but because there is no legal protection for parking in a space, only the right to park there, the majority of car park operators have not signed-up.
Bert Morris, AA motoring policy manager said: 'The Secured Car Parking Scheme, which the AA fully supports, is not having the take-up the police, Government and motorists want because too few operators have embraced it.
'No wonder, when the law is totally on the car park operators' side. The law is now the only option. We must ensure better standards across the board and to give motorists a fair deal.'
When launched in 1999, it was hoped more than 2,000 operators would have signed up to the minimum standards by the end of last year. These include lighting, signing, access, safety, design and ticketing.