The government came under fire this week after fines handed out to uninsured drivers fell by a quarter over a decade.
Liberal Democrat MPs claimed there was no incentive for drivers to take out insurance with fines being cheaper than buying cover.
Official figures obtained by the Liberal Democrats show the average fine handed to an uninsured driver has fallen by 25% from £224 in 1997 to £169.
At the same time insurance premiums have almost doubled. The AA has compiled a basket of insurance quotes since 1994, covering 500 varied risks and more than 50 insurers. Its average has risen from £429.07 in July 1997 to £822.47 this year.
Liberal Democrat shadow transport secretary Susan Kramer said: “By fining offenders significantly less than the cost of insurance, the government is hardly sending out the right message to uninsured drivers.
“Much more needs to be done to catch and prosecute uninsured drivers, whose actions cost law-abiding drivers thousands of pounds a year.
“These figures are bad news for law-abiding motorists. Unless the government can reverse this trend all drivers will pay the price.”
The AA said uninsured drivers added £30 to each motor premium.
The Liberal Democrats argue that the huge number of uninsured drivers on the roads cause a disproportionate number of accidents and a Commons debate is needed to ensure ministers listen and act.
Courts are allowed to hand out fines of up to £5,000 to anyone found guilty of driving while uninsured.
The government said it was committed to the problem and measures were in place if courts chose to hand out the maximum fines.
A Department of Transport spokesman said they took driving while uninsured very seriously and said the government was continuing to clamp down by introducing new legislation, including the offence of being the registered keeper of an uninsured car.