Some 43 per cent of motorists never wear a seat belt, according to the National Safety Council (NSC).
Announcing a new seat-belt campaign entitled "Clicked Yet?", the safety council has also revealed that 80 per cent of back-seat passengers are never buckled up.
This is exacerbated by the fact that many back-seat passengers are children being transported to and from school.
According to Mr Pat Costello, chief executive of the NSC, a survey conducted in 1999 revealed that 57 per cent of motorists used their seat belts and as many as two out of three men never buckled up.
Without a seat belt, three out of four people in a 30 m.p.h. head-on collision will be killed or seriously injured, he says.
Use of seat belts in the Republic has consistently failed to reach targets of 85 per cent and lags behind many of our European neighbours.
The campaign is directed at all car-users but aims to get specific messages across to male drivers, who are 20 per cent less likely to use a seat belt than females.
In addition, some mature drivers may be unfamiliar with the legal requirement to wear a belt in front and rear seats.
"Clicked Yet?" is part of a wider NSC seat-belt campaign set to run from the May bank holiday weekend through the summer encouraging motorists to take road safety seriously for all car journeys, both long and short. The NSC points out that 15 people died in road crashes over the St Patrick's and Easter bank holidays.
The Garda Síochána has warned that enforcement of the law on seat belts will be stepped up over the May bank holiday.