Mr Goodwill was featured on the BBC One programme Cars, Cops and Criminals on Wednesday in which he showed just how easy it was to clone number plates – by buying the same registration number as the Prime Minister.

He went to Downing Street to find out what Gordon Brown's registration number plate was and then ordered a cloned copy on the internet for just £20.

He was contacted by the BBC after raising the issue in the Evening News and on his website, and a film crew spent a day with him at his London office.

Mr Goodwill said: "The problem is there is a massive loophole in the regulations which means as long as you sell a number plate as a showplate you can supply them to anyone on the internet."

Showplates are plates carrying words, letters or numbers dictated by a customer online or over the phone, which are theoretically only used off-road, at events like motor shows or in car showrooms.

But police chiefs say there is absolutely no difference in size, materials or lettering between genuine registration plates and most showplates.