Holidaymakers are being warned about fraudsters who place false adverts on accommodation websites, conning them out of hundreds of pounds.
Last year, some 4,700 travellers fell victim to such scams, which included fake airline tickets.
On average those affected lost £1,500 each in 2017, according to the police, a 25% rise on the year before.
In many cases the fraudsters hack into accommodation websites and ask to be paid directly.
But as soon as payment is made, they disappear.
The Association of British Travel Agents (Abta) is also warning about fake airline tickets that never arrive. Last year, most of the flights concerned were to Africa or Asia.
'I was petrified'
Last May, legal secretary Georgia Brown tried to book a holiday in Amsterdam for herself, her partner Jamie, and some friends.
She spotted an advert on an accommodation website, where the owner of the apartment was asking for a deposit of £915.
She corresponded with the man by email, and then sent the money off by bank transfer.
But she never heard from him again.
"At the time I was petrified. I thought someone had hacked into my bank account. It was really scary," she said.
She was also critical of the booking site involved.
"I just don't understand how this person was allowed to advertise on the website."
Georgia Brown eventually got her money back through her bank.
In order to avoid being conned, Abta advises holidaymakers to:
- Do research. Check the holiday company's credentials, and look at several reviews of the property involved
- Check the web address is legitimate, and has not been altered. For example from co.uk to .org
- Be cautious about paying directly into an individual's bank account. Bank transfers are like paying by cash, so are difficult to trace. It is safer to use a debit or credit card
More than half of the victims of travel scams told Action Fraud that the experience had affected their mental health or financial well-being.
In some cases the impact was even more serious.
"The startling emotional impact of falling victim to holiday fraud is highlighted in the latest figures, as 575 people reported that the harm to them was so severe, they had to receive medical treatment or were at risk of bankruptcy," said Pauline Smith, head of Action Fraud.
It follows earlier warnings this year about so-called "chalet fraud" for people booking ski-ing holidays.
On average those who were tricked into sending off money to reserve a chalet lost more than £2,000 each.