ANNOYING back-seat drivers are more likely to cause an accident than prevent one, according to a poll.
Motorists said that the most annoying passenger habit was giving directions or commenting on driving technique.
Other irritating habits included talking too much, fiddling around with the car stereo and talking or texting on mobile phones.
The same study found that husbands and wives are the most irritating passengers.
Most drivers get so annoyed with their partners or spouses that they would prefer the company of a hitchhiker.
Conor Faughnan, director of policy with AA Roadwatch, said that he was not surprised by the findings and urged passengers to "shut up and let the motorist concentrate on driving".
"It can be very distracting and irritating when your partner keeps on talking," he told the Herald.
"Whereas if a stranger is in the car, he or she will be far more constrained and less likely to make any comments.
"Passengers should remember they're not driving the vehicle and they should let the driver get on with the driving.
"If they keep on making comments, they are more likely to cause an accident rather than prevent one.
"So my message would be that, for the most part, when the driver is driving, passengers should just shut up and let them drive."
The survey by Confused.com, the price comparison website, found that one in five motorists polled had been in an accident while travelling with someone else in their car.
And almost one in 10 of them later blamed it on that person's behaviour.
More than a third of drivers said passengers affected their behaviour at the wheel and one in five admitted they became more distracted when someone else was in their vehicle.
Motorists said parents were their least favourite car companion, with husbands and wives a close second.
However, three-quarters of those polled said their driving improved and they slowed down when children were in their car.