BRITAIN has the highest prices for more than three-quarters of the best-selling cars in the European Union according to the findings of an investigation published in Brussels yesterday.

The European Commission-sponsored survey revealed that British drivers pay more than any other in Europe when purchasing 60 of the 74 most

popular models.

At the other end of the spectrum, the best deals appear to be in the Netherlands, where prices were found to be the lowest for 34 makes of car.

British motorists looking to buy a new Mazda 121 or a Rover 214, 414, or 620 will find themselves paying half as much again as the cheaper prices on the Continent.

The investigators did discover, however, that since the last survey in November the cost of several models on the British market had fallen: for a Peugeot 106 by 7%, a Ford Escort/Orion by 11% and a Renault Megane by 16%.

But what surprised them were the price disparities between the same models on the British and Irish markets.

In many cases these were around 25% and in some instances, notably for certain Rover, Honda and Fiat models, as high as 40%.

''In Ireland, the Netherlands and Portugal where special car taxes are due, net car prices are among the lowest for a large number of models,'' noted the Commission. ''On the other hand, in countries such as the UK, France and Germany where no such taxes are due, pre-tax prices tend to be

higher.''

The wide differences in prices has encouraged many British motorists to try and purchase right-hand drive cars in Ireland and on the Continent.

The Commission warned yesterday that it would consider taking legal action against any motor manufacturers which tried to prevent drivers from benefiting from lower prices outside the country.