She explained: "A high-street policy is designed as a one-size fits all in most cases. It doesn't provide cover for people with pre-existing medical conditions, so it excludes them from medical cover.
"But there are plenty of specialist insurers out there, so it is a case of going to one of those, and shopping around."
Ms Ostler's comments on the issue have come after research by charity Cancerbackup last year found that 70 per cent of cancer sufferers found the experience of finding travel insurance distressing.
The ABI is the insurance industry's biggest trade association in the UK, with around 400 member companies.
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.