British travellers are having to shop around in some resorts to find bureaux de change where sterling cheques are accepted.
The AA is advising people travelling abroad to take credit and debit cards where possible as a precaution.
A Foreign Office spokesman played down the problem. 'There haven't been thousands of people coming on to us. It's only some banks,' he said. He suggested that tourists who have trouble take their travellers cheques to larger banks.
Thomas Cook said it was aware of some 'mainly isolated incidents' - and had received complaints about rates being offered.
A spokesman advised holidaymakers to buy travellers cheques in the local currency or buy foreign money here and take it with them.
Andrew Johnson, AA Travel and Information Services director, said: 'Credit or debit cardholders can also of course use cashpoint machines to draw currency, which is quicker than queuing at banks.'