Motorists caught driving without insurance are getting an easy ride from the law, it has been claimed.

The size of fines slapped on offenders by Sussex magistrates has decreased over the past few years, official figures show.

In 2000 the average penalty was £167. By 2004, the latest period for which figures are available, this had fallen to £162 - a fraction of the cost of an insurance policy.

Over the same period, the number of people convicted in Sussex fell from 3,808 to 3,102.

Home Office figures obtained by the Liberal Democrats show that, across England and Wales, the average fine handed to uninsured drivers in court fell by 16 per cent, from £203 in 2000 to £169 in 2004.

Lib Dem Transport spokesman Paul Rowan criticised magistrates for sending out the "wrong message".

He said: "The Department of Transport and Home Office need to get their act together and do something. The problem of uninsured drivers needs to be given a greater profile and fines need to be larger.

"Fines should be increasing not decreasing. There are huge number of uninsured drivers on the roads who cause a disproportionate number of accidents. We need a Commons debate - then ministers will have to listen and act."

Courts are permitted to hand out fines of up to £5,000 to anyone found guilty of driving without insurance. They can also impose up to eight penalty points.

Since 2003, the offence has also been punishable by an on-the-spot fine of £200 and six penalty points, as an alternative to prosecution. These cases are not included in the Home Office figures.

Transport minister Stephen Ladyman has admitted the Government does not know how many people are driving without insurance.

But the RAC Foundation estimates uninsured drivers may account for five per cent of all motorists.

A Department of Transport spokesman said: "Stephen Ladyman has been extremely clear on what he thinks of uninsured drivers. He believes it is unacceptable and we do take the matter extremely seriously.

"There are already laws in place to crack down on uninsured drivers and we have introduced more."