The RAC says motorists are confused about parking rules

The motoring group says that figure could rise if the Traffic Management Bill - giving parking attendants increased powers - is passed.

The research from RAC legal experts also suggests more 30% of drivers are confused by parking restrictions.

The group is warning the government to address the issue before the traffic bill becomes law.

Under the proposed new jam-busting measures, traffic wardens will get powers to fine motorists who jump red lights or illegally block junctions.

Transport Secretary Alistair Darling said police time would be freed up by switching powers to local councils.

If traffic attendants are to take on further roles, it is clear that motorists' confusion needs to be addressed first Eddie Ryan, RAC

But the Tories have already warned the move to give greater power to traffic wardens could fuel further resentment from motorists already angry about the proliferation of traffic cameras.

RAC legal services managing director Eddie Ryan said: "Parking attendants already have the unhappy status of being despised by motorists.

"If their increased powers are not used with common sense, it could lead to even more confrontation with angry motorists who feel they've been unfairly ticketed."

Red lines

The RAC says more than 60% of drivers are muddled about the difference between parking on red and yellow double lines.

Almost a third (32%) admitted to parking on a double yellow line and 5% on a double red line.

Mr Ryan said: "Clearly, the restrictions on where you can and cannot park leave motorists unsure of where they can leave their cars.

"With red lines in London, there are already four different types of parking line restrictions and that doesn't take into account the increasing number of resident permit parking restrictions or bus lane restrictions.

"The government is keen to tackle congestion but, if traffic attendants are to take on further roles, it is clear that motorists' confusion needs to be addressed first."