FG Senator Fergal Browne has claimed that only 25% of motorists reported to gardaí under the Traffic Watch scheme have been given formal cautions.
Mr Browne claimed only 1,000 of the 3,800 people reported under the scheme since its establishment in November 2001 had received a caution.
He said this was evidence that the scheme was not being implemented rigorously enough.
Traffic Watch was established to enable people to inform on motorists who breach the rules of the road.