Car hire firms have defended increases of up to 240 per cent in rental charges over the Christmas period.
The Consumers Association surveyed four of the main car hire companies and found that rates rose dramatically over the festive period compared to the first half of December.
Prices were increased by as much as €496 for hiring a small car from Dublin airport for a two-week period, the survey found. The mark-up on cars rented from Belfast airport was much smaller and there was no increase in prices for cars rented from Paris airport before and during Christmas.
However, car hire companies said the reason prices went up over Christmas was because there was so much demand at an otherwise quiet period for business, in mid-winter.
Greg Turley of Argus Car Hire said: "Car hire in Ireland is 90 per cent tourism-related. When there are no tourists, there is no business, but at Christmas, we go from the worst time of the year, when vehicle stocks are low, to the peak time.
"There are only so many cars to go around."
Mr Turley said the car hire industry was very labour intensive and margins were tight. The reason why there was a higher price difference in Dublin compared to Belfast and Paris was because the demand driven by returning emigrants.
In the survey, published in Consumer Choice magazine, Avis quoted €258 to hire a compact five-door car in the first two weeks of December, but €546 over the Christmas period, an increase of 112 per cent.
The Hertz tariff for the same car category rose from €292 to €690, a rise of 136 per cent. Argus's rates went from €218 to €590, an increase of 171 per cent. Budget quoted the cheapest price in early December, €209, and the most expensive over Christmas, €705, an increase of 237 per cent.
Belfast was more expensive than Dublin in early December but cheaper over Christmas. The increase for Avis was 22 per cent, Hertz 44 per cent, Budget 50 per cent and Argus 53 per cent.
Consumers Association chief executive Dermott Jewell said: "We appreciate that demand for hire cars is high at this time of year, but even the conventional laws of supply and demand are being ruthlessly stretched here.
"What is it about car hire firms in the Republic that they feel they can double or treble in the space of a week? Particularly when branches of the same firms in Belfast or Paris airports only raise prices marginally or not at all in the same period?"
The survey also uncovered significant variations in car hire prices between different firms. For example, the cost of hiring a Toyota Avensis for a week in October varied between €162 through Argus to €279 with Hertz.
