There are about one million unlicensed vehicles nationwide

The city is being used to pilot a new enforcement line which will be available nationwide over the coming months.

There are currently about 187,000 unlicensed cars on London's streets - worth more than �21m in lost revenue.

Many are involved in crime and they are often uninsured.

It is hoped the new tip-off line, which was announced by transport minister David Jamieson at Earl's Court, will help catch more tax evaders.

'Make offenders pay'

Mr Jamieson said: "By ensuring vehicles do not fall out of the registration system, we can reduce the number of unlicensed and often uninsured vehicles on the road, tackling car abandonment and bringing dishonest motorists to book.

"These new measures will protect the majority of honest and responsible motorists, make the system more secure and make the offenders pay."

The government estimates the national cost of uninsured driving is �500m - or up to �30 to the legitimate car owner's annual insurance premium.

Other measures to tackle car crime, car dumping and to ensure that every vehicle has a traceable owner will also be announced.