BMW has raced to defend the new convertible version of the Mini against criticisms from driving examiners.

The convertible, whose popularity has further boosted already rocketing worldwide sales, has been banned from tests due to poor visibility.

But German manufacturer BMW, whose Cowley plant is soon to receive a massive £100m investment to keep up with demand for the marque, say the move is "unfair".

The car has been banned from driving tests because of the restricted view from the front passenger seat -- the first time in the 70-year history of the driving test that a car which is legal on the road has been outlawed.

The Driving Standards Agency, which regulates the tests, imposed the ban after examiners complained that they could not see clearly out of the back window because of the roll bars behind the rear passenger seats.

A DSA spokesman said: "There is nothing wrong with the car in normal circumstances, but a test examiner needs to be able to see all round."

New cars have to pass a series of safety tests before they are allowed on the road, but there are no regulations affecting rear visibility.

But the ban could have implications for other convertibles, whose folding hood mechanism often impairs all-round visibility. The convertible Mini was launched nine months ago and 15,000 have been sold in the UK.

BMW spokesman Lizzie Graymore said: "Other cars in the same class as the Mini have blind spots, and it seems unfair to single out the Mini. Obviously the Mini passes all safety regulations and we disagree with the DSA's view."