Motorists will face a "recipe for confusion" when new parking measures are introduced next month, according to the British Parking Association (BPA).
The organisation fears the new measures, which are to be introduced on October 1, do not go far enough and do not provide sufficient protection from rogue parking operators.
There will be a number of significant changes to the way that parking on private land is managed in the Protection of Freedoms Act, including a ban on clamping and towing away on private land, as well as a new independent appeals service.
The BPA is warning that motorists are not likely to realise that, in each case, they will not necessarily be better off than they were before.
The ban on clamping and towing away applies only on private land, and even then there are a number of further exceptions where by-laws give landowners the right to manage their parking in any way they choose.
These include car parks at railway stations, airports and port authorities.
Those within the industry have argued that the ban on clamping will not protect motorists at all and that rogue operators will simply turn their hand to illegitimate ticketing.
Chief executive of the BPA, Patrick Troy, said: "The Protection of Freedoms Act ushers in perhaps the most significant shake-up of the private parking industry ever seen in this country and there is much that we and the Government can be proud of.
"However, the regulations do not yet go far enough. An independent appeals service which is not binding on all operators is likely to be a recipe for confusion among motorists and a ban on clamping is no substitute for proper regulation of the industry.
"That being said, the new appeals service, such as it is, will provide a long overdue layer of protection for motorists who want to know that they no longer have to look to the courts for recourse when they feel that a parking enforcement notice has been unfairly issued."