The Foreign Office is advising caravanners to instal alarms after a string of tourists in France were gassed and robbed as they slept.
It is also suggested that they stay only on official campsites after Britons who had parked overnight at roadside rest areas had valuables stolen, apparently after gas was pumped into their vans to render them helpless.
In the most recent incident, an elderly couple who had parked in a lay-by near La Croix Valmer, in southern France, woke to find £1,200 in cash stolen as well as their passports, bank cards, mobile phones and satellite navigation system.
Diane Bezer and Geoff Sillito believe thieves piped sleeping gas through the vents of their camper van, knocking them out so they could raid their camper van without fear of being disturbed.
Mrs Bezer, of Winterbourne Bassett, Wilts, said: "When we woke up everything was gone and we had a really woozy feeling. The gas had an effect because we didn't wake up until 9am and we are usually awake at 7am.
"We carried on with our holiday but it was ruined. I couldn't sleep at night after it happened because I kept thinking I was breathing gas. I still feel traumatised and can't get it out of my mind."
A spokeswoman for the Foreign Office said there had been a number of reports about British holidaymakers being gassed and then robbed across France in recent years, mainly when they had parked in lay-bys and rest areas.
She added: "There have been enough cases to warrant us mentioning it in our travel advice."
The Foreign Office's advice on crime in France now states: "There is also a continuing problem of burglaries taking place during the night whilst travellers have been asleep in their caravans, mobile homes or other vehicles.
"Thefts have occurred in rest areas on the A25 (Dunkirk to Lille) and A16 (Calais-Dunkirk) motorways. In some cases, victims had first been rendered unconscious by the thieves using gas. Try to avoid parking in isolated or dark areas of camping grounds or car parks, and consider installing an alarm in your caravan or mobile home."
The Caravan Club said it had also received reports from victims and advises British tourists not to stay overnight in roadside rest areas known as Aires de Service, where most of the crimes are thought to have taken place.
A gang of thieves has repeatedly raided a French store chain for the past four years and stole money from its safes by using powerful vacuums.
The Sun reports that the burglars have recently pulled the fifteenth such hit against Monoprix supermarkets located around Paris.
Their routine involves drilling a hole into the pneumatic duct used to carry rolls of money from checkout to the safe and then literally suck the cash out with a vacuum.
The most recent raid took place last Monday at the Monoprix store on Garibaldi Street in Saint-Ouen. The thieves, which the police now call the "Vacuum Burglars," broke in through an emergency door.
This time, the vacuum-armed plunderers did their thing and walked away with over 70,000 euros (almost $100,000).
The CCTV cameras captured everything, but since they were wearing ski masks, identification from the footage is unlikely.
"They spotted a weakness in the company's security system and have been exploiting it ever since," a French police spokesperson told The Sun.
"Since 2006 they have stolen more than 500,000 euros and caused damage to alarm systems and other property totaling thousands more.
"It is clearly time Monoprix addressed this loophole and changed the way it guards its money," he added. The supermarket chain refused to comment on the incidents.
Apparently, on one occasion the thieves were unintentionally caught by a employee, who returned to the store after hours.
However, they escaped after threatening him with a handgun, which suggests that they are experienced and prepared to deal with unforeseen situations.
This case stands to show that criminals will not hold back from exploiting any little security hole or business logic flaw they can in order to make a profit.
The most recent similarly ingenious crime we reported involved a group of UK fradusters, who bought iPhone subscriptions using stolen identities and then shipped the SIM cards to other countries where they were used to call premium-rate numbers non-stop.
Police in France are looking for two attractive female thieves who bared their breasts at a man at a cashpoint to distract him before stealing his money.
The women in their 20s exposed themselves to the victim as he punched his pin code into an ATM machine in Paris.
As he stared at one, the other then withdrew 300 euros from his account before the pair fled with the money.
The incident was captured on CCTV at the cash machine on Paris’s Left Bank, but the women could not be identified, a French police spokesman said.
“We would advise anyone withdrawing cash from a machine to focus on what they are doing and not allow themselves to be distracted, however attractive the view,” the spokesman added.
French winegrower loses entire crop to thieves
Thieves used own grape-harvesting machine and lorry to transport 30 tonnes of grapes spread over two hectares
For one French winegrower 2010 will not be remembered as a vintage year. The farmer awoke one morning this week to find thieves had broken into his remote vineyard and stolen his entire crop of Cabernet Sauvignon grapes.
The thieves struck last weekend at the vineyard in Villeneuve-lès-Béziers. They arrived with their own grape-harvesting machine and a lorry big enough to transport the 30 tonnes of grapes spread on vines over two hectares.
"The thieves took advantage of a night when the moon was full to commit their crime," said the winegrower, Roland Cavaillé, who said he had lost an entire year's work and a harvest worth