So says moneymaxim.co.uk after the company's research revealed that while car rental firms strive to be the most competitive on price comparison sites by reducing prices, they are stealthily increasing the level of excess charges a driver remains liable for.

According to the firm, in major tourist destinations such as France and Italy these excesses are commonly reaching €1,500. However, the moneymaxim study has shown that new highs are being reached in Australia, where a Sydney rental from CarHire3000, part of the Travel Jigsaw group, could, where single vehicle accidents are involved, result in excesses of up to Aus$7,700 (€5,615) being charged.

Mark Bower, managing director at moneymaxim.co.uk, said: 'This year we have seen new heights in the level of excesses that car hirers are being charged by car rental companies. Whereas in the past these may have been a few hundred pounds they are now, in many instances, well over a thousand pounds.

'This also has the added benefit to car rental firms of making the refusal of their "excess protection policies" more difficult when drivers discover the potential charges they can be liable for in the case of an accident or theft.

'The price of their excess protection policies can now often be in the region of €15 a day. Not only is this excessive – sometimes eclipsing the charge of the car hire itself – but the policies often exclude a number of potential areas of claim, such as punctures, windscreen or mirror damage too.'

The firm added that many of these car rental companies have limited excess cover on their policies, meaning drivers involved in an accident or having their car hire broken into or stolen can still be severely out of pocket even if they have purchased excess protection policies from car rental firms.

Mr Bower concluded: 'We really recommend car renters look carefully at their rental agreement well before they travel – that way they can check what excesses apply and obtain cheap cover if they wish to. It also removes any pressure to buy additional expensive products whilst standing at a foreign rental desk – a situation many of our customers say they have found themselves in.'