Package tour operator, Holidays 4 UK, has gone bust, leaving hundreds of thousands of people with summer holiday plans in limbo.

The major holiday company, based in Brighton, which also traded Holidays 4U, sold package holidays and flight-only deals to Turkey, mainly from Belfast

Its collapse will affect 12,800 customers already in Turkey, while 50,000 more with bookings were told their trips would probably be cancelled.

It is estimated about 300 people from Northern Ireland are currently in Turkey with the firm. They should be able to complete their holiday and fly home as planned.

They are advised to check in for their flights as normal. They have been warned that while the Civil Aviation Authority will get them all home, they might not be able to return to their designated airport.

It is thought that about 2000 people from Northern Ireland who were due to travel with the company will now have to seek a refund, which will be administered under the Air Travel Organisers' Licensing Scheme (Atol).

Passengers who have booked through a travel agent have been advised to speak to their agent in the first instance.

Also trading as Aegean Flights, the operator flew from a number of UK airports, including Belfast, Cardiff, Bristol, Gatwick, Edinburgh and Glasgow. The company generally used Onur Air, a Turkish low-fare airline.

Holidaymakers were warned that more companies would go bust this year because of cut-throat competition in the travel industry.

Travel journalist Simon Calder told Metro: “If you have a substantial tour operator going bust so early in the summer it’s difficult to say they’ll be the last.”

He said Holidays 4 UK was a victim of intense competition in the industry and because its prices were simply too low.

“You and I are not prepared to pay enough money to keep them in business,” he added.

“The best thing the 12,800 people currently on holiday in turkey can do is sit by the pool and order another drink.”

Holidays 4 UK failed because of the economic downturn, said Ian Oakley-Smith, joint administrator and director at PricewaterhouseCoopers (PwC).

"The company has suffered because of the difficulties faced by the travel industry during 2010 and 2011,” he said.

Oakley-Smith confirmed the company would cease operating immediately and most of its 18 staff had been made redundant.

A rival operator to Holidays 4 UK is currently offering a week’s holiday on the Greek island of Kos for just £139 – including return flights from Gatwick and accommodation.

“In the middle of the summer holidays that’s just completely unsustainable,” said Mr Calder. “They’re simply selling below cost.”

Atol spokesman David Clover said: "There is never a good time for a travel firm to fail; unfortunately the height of summer is the worst possible time."

Holidays 4 UK had an annual turnover of about £35m.