Tour operator Seguro Travel has ceased trading today.
The Cheshire-based company also traded as Seguro Holidays, Kent Escapes, KentEscapes.co.uk and KentEscapes.com.
ABTA understands there are 2,400 people abroad with Seguro Travel and 17,253 forward bookings up until the end of summer 2009.
Most passengers would have flown from Kent or Scotland.
As the company had an ATOL licence, customers are asked to contact the Civil Aviation Authority. See www.atol.org.uk or email claims@cpg.org.uk.