LONDON Britain's third largest package holiday operator, XL Leisure Group, said on Friday it had gone into administration and grounded all flights, leaving thousands of holidaymakers stranded.

In a statement on its website, XL said its companies, which include Kosmar Villa Holidays and The Really Great Holiday Company, had suffered from volatile fuel prices, the economic downturn, and being unable to obtain further funding.

Alastair Beveridge, Nick Cropper, Simon Appell, and Stuart Mackellar have been appointed joint administrators.

'The joint administrators cannot continue trading the business and therefore all flights operated by the companies have been immediately cancelled and the aircraft grounded.

Going forward, the joint administrators are unlikely to be able to trade the business or operate the aircraft,' XL said.

XL advised all passengers who have yet to begin their journeys to make alternative arrangements.

Customers who booked a package holiday will have the cost of getting back home reimbursed through a scheme operated by Britain's Civil Aviation Authority but those who booked flights only are not protected by the scheme.

TUI Travel, Europe's biggest travel firm, said in a statement it was trying to help XL's customers stranded abroad get back to the UK.

However, TUI Travel's Chief Executive Peter Long criticised the inconsistency in the protection for holidaymakers.

'We at TUI Travel will help where we can but it is time the government realised that there needs to be a level playing field for all providers of overseas leisure travel arrangements.

Unfortunately, many people think they will be protected when this arises and this is not the case,' he said.

Earlier this week, Spanish charter airline Futura International, which is Europe's biggest independent medium-haul charter airline, also filed for administration.

XL, which had undergone a management buyout in recent years, ranked third behind TUI Travel and Thomas Cook in UK holiday groups.

Shares in TUI Travel were 4.1 per cent higher at 230-3/4 pence at 0705 GMT, with Thomas Cook up 3.5 per cent to 243-1/4 pence, investors expecting them to gain from decreased competition in the marketplace.