The number of holidaymakers ripped off by booking scams rose by almost a fifth last year, new figures show.
There were 5,826 reported cases in 2016, up 19% on the previous year, according to the UK's national fraud and cyber crime reporting centre ActionFraud.
The most common scams related to airline tickets, online accommodation bookings and timeshare sales.
A total of £7.2 million was lost last year, at an average of £1,200 per victim.
More than a quarter (26%) said the scams had a significant impact on their health or financial well-being, while 259 were left needing medical treatment or at risk of bankruptcy.
Fraud prevention group Get Safe Online, travel trade organisation Abta and City of London Police have launched a campaign warning of the dangers posed by holiday booking fraud.
Tony Neate, of Get Safe Online, said holidays are often a "big-ticket item" and present "the perfect opportunity for cyber criminals to swindle unsuspecting victims out of their hard-earned money".
He went on: "Always do as much research as you can about the organisation you're booking through, and ensure that they are a reputable travel operator that is a member of a recognised trade body like Abta.
"By booking in haste, you could not only risk losing a huge amount of money, but also disappoint family and friends when it comes to that long-awaited escape."
Sporting and religious trips are a popular target for conmen due to the limited availability of tickets and subsequent higher prices.
Fraudsters are setting up bogus accommodation websites, hacking into legitimate accounts and posting fake adverts online.
Holidaymakers are also losing thousands of pounds by booking flights and not receiving genuine tickets. Flights to Africa and the Indian subcontinent were targeted last year.
Action Fraud says reports of travellers being swindled have consistently risen over the past five years.
Authorities believe criminals are taking advantage of travellers' lack of awareness of the strict regulations in place for UK-based travel firms.
The majority of those who are defrauded pay by methods such as bank transfer or cash, with no means of getting their money back.
Fraudsters are actively encouraging these payment methods by claiming they are the only ones protected by their own bogus insurance schemes.
Abta chief executive Mark Tanzer said: "Abta is regularly contacted by members of the public who have been caught out by increasingly sophisticated travel-related frauds.
"We know at first-hand that the loss and shock of finding that your flight or holiday accommodation has not been booked can be very significant.
"Follow the tips we have put together in partnership with the City of London Police and Get Safe Online to avoid falling victim and to make sure your hard-earned money goes towards your holiday and not lining the pockets of an unscrupulous crook."