British cruise company All Leisure Holidays has collapsed, leaving hundreds of holidaymakers stranded abroad.
The firm operates under the Swan Hellenic and Voyages of Discovery brands, which both called off New Year cruises at short notice.
The group is protected by the industry's Atol insurance scheme, which means that passengers abroad will be flown home free of charge.
The Civil Aviation Authority (CAA) will help to repatriate the 400 holidaymakers who are currently abroad, but future bookings for 13,000 people have been scrubbed.
The majority of the customers who are aboard are currently near Malaysia and around the Mediterranean, the CAA said.
Travel trade body ABTA told customers on its website that remaining All Leisure Holidays trips "are now cancelled and your booking will not go ahead".
Voyages of Discovery's 540-passenger vessel Voyager was due to sail from Port Kelang in Malaysia on Wednesday (4 January), on a sold-out 15-day trip to Singapore. Minerva, the 350-passenger ship operated by Swan Hellenic, should have departed from Marseille on Tuesday (3 January) on a 15-day trip to Tenerife.
Andy Cohen, Head of Atol at the CAA, said: "We understand this will be concerning news for anyone who has booked to travel with the company.
"However, the Atol scheme exists for exactly this kind of situation and we are making immediate arrangements so all Atol-protected customers can claim full refunds as quickly as possible. We are also arranging for people currently overseas to get back home to the UK at no extra cost – meaning no-one will be left stranded abroad."
Grant Thornton will take over the administration of All Leisure Holidays, which ran two ships, and turned in sales of £60m in the year to October. The group, based in Market Harborough, Leicestershire, employed 150 staff with most expected to be made redundant.
ABTA said customers who require further help should contact it on: 020 3758 8742.
Further information is available at www.atol.org.uk and a refund claim form will be available shortly, the CAA said.