Since April, 12 tour operators have collapsed with four going under in the past month, according to a report.
All firms were members of travel protection scheme Air Travel Organisers' Licensing (ATOL) so customers can claim refunds for cancelled trips or get home if stuck abroad, according to the Sun.
Roger Mountford, chairman of the Air Travel Trust Fund which backs ATOL, said: "An increase in the number of insolvencies is an indicator of tougher trading conditions."
He went on to say that the recent events could be an indication of more deterioration later this year.
The Civil Aviation Authority recommends that anyone booking a holiday checks the firm they book with is ATOL protected.
Last December, travel firm Travelscope Holidays collapsed due to cash flow problems, the Telegraph reported at the time.
Up to 40,000 people were affected by the collapse of the company, including 10,000 due to travel over Christmas alone.
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