One in five holidaymakers is travelling overseas uninsured, according to new research.

They run the risk of substantial medical bills which can run into thousands of pounds, particularly if an air ambulance is required to fly them home, travel association Abta warned.

The percentage doing this is similar to last year, when 22 per cent travelled overseas uninsured - but there has been a big rise in young holidaymakers doing so.

One third (33 per cent) of 16-24 year olds are travelling uninsured, up from 22 per cent in 2014.

A similar proportion (32 per cent) of 25-34 year olds are also doing this, making these two age groups the most at risk should something go wrong.

Abta said confusion among young holidaymakers over what a European Health Insurance Card offers may be partly responsible for them not taking out insurance.

More than one in five (22 per cent) of 16-24 year olds believe they do not need travel insurance because they have an EHIC. While EHICs, which need to be renewed every five years, will give access to emergency state medical care throughout most of Europe, it is not a substitute for travel insurance.

"EHICs will not cover the cost of repatriation to the UK in an air ambulance, private medical care or additional expenses, such as accommodation for family staying in resort," an Abta spokesman said.

Financial constraints may also be responsible for the increase in numbers travelling uninsured, with 30% of all respondents with children saying cost is the principal reason they do not take out insurance.

Abta chief executive Mark Tanzer said: "It is a real concern that we see so many travellers telling us that they have recently gone overseas without travel insurance. Every year we come across tragic incidents of people having accidents or falling ill overseas without travel insurance and then having to pay bills which can quickly run into thousands of pounds.

"Often they are younger travellers and their families are left with the burden of having to pick up the bill. Whatever your financial circumstances may be, avoiding taking out travel insurance is a very false economy."