As a Spanish hotelier reveals a 50-fold surge in holiday sickness claims, the Foreign Office has warned tourists to Portugal that fraudulent claimants could face prosecution.

Sebastian Darder, a hotelier in Mallorca, told ITV’s Good Morning Britain that claims from UK holidaymakers for gastric illnesses increased from seven in 2015 to 350 in 2016.

The number of claims has soared because of a change in the law that caps legal costs for personal injury cases in the UK. Holiday illness cases that occur abroad are not covered by the limits.

Many companies have sprung up in Britain to persuade returned holidaymakers to make retrospective sickness claims on a no-win, no-fee basis.

A Cheshire-based claims-management firm trading as Sickholiday.com advertises on radio and TV, using lines such as: “If your scenic view was the bowl of the loo, click sickholiday.com.”

The company tells claimants: “If you win your case, the only thing you will have to contribute is 25 per cent of the compensation you are awarded, leaving the tour operator to pay for your entire solicitor’s entire basic charges and expenses.”

But of particular concern to the travel industry is the number of touts in resorts in Europe who are seeking to drum up business by promising thousands of pounds.

As The Independent has reported, some touts sit outside Spanish hotels in “ambulances”, promising holidaymakers payouts running into thousands of pounds and coaching them about the “evidence” they need to support a claim.

In a bid to drive down the number of claims Some hoteliers have threatened to remove the all-inclusive option. Touts typically urge holidaymakers to say they have eaten only in their hotel.

Now the Foreign Office has issued a bulletin aimed at visitors to Portugal, warning: "If you make a false or fraudulent claim, you may face legal proceedings in the UK or Portugal.”

The new travel advice says: “There have been reports of an increase in holidaymakers being encouraged to submit a claim for personal injury if they have experienced gastric illness during their stay.

“You should only consider pursuing a complaint or claim if you have genuinely suffered from injury or illness."

Jet2 has sent undercover investigators to Spanish resorts to gather evidence about the touts’ operations.

“It’s become the new timeshare scam,” said Humphrey Carter, editor of the Majorca Daily Bulletin. He has done some undercover filming for a Spanish TV station on the topic.

Mr Carter told The Independent: “They’ve got touts in resorts and bar-owners on the payroll. They’re trying to convince people to make a claim on a no-win, no-fee basis, and it’s a cash bonus all round.”