Motorists are being made aware of a little-known rule in place at Tesco petrol stations.

While filling up your vehicle with fuel should be fairly straightforward, those looking to fill up anything should be wary.

Because it turns out that there are strict rules in place by the supermarket.

It is not widely known but anyone looking to fill containers can only fill up a maximum of two, and they must not exceed 30 litres between them.

A Tesco spokesman said: “Under the Petroleum Consolidation Regulations, we are required to have a policy in place to ensure the safe use of portable fuel containers at our petrol stations.

“Our policy is that only two portable containers (with a maximum combined capacity of 30 litres) may be filled on each visit by a customer.”

It comes as a Wiltshire man complained to the retail giant after being threatened with being reported to police for filling up three jerry cans full of petrol last year.

Malcolm Cupis, from Keevil, said he was “rudely accosted” by a kiosk assistant at the Tesco Extra store in County Way, Trowbridge, on a weekend visit in March.

He says he was threatened with being reported to police for ‘illegally’ filling three standard five-litre jerry cans after also putting fuel in his 42-year-old ex-Army Land Rover Gloria.

Mr Cupis,54, of Martins Lane, said: “I went to the Tesco Extra filling station to put fuel in my Land Rover and to fill up the three cans for my old classic motorcycles and my lawnmower.

“I was busy filling the cans when the pre-paid pump was turned off and a woman came out of the kiosk and told me I would be reported to the police.

“She came across the forecourt and shouted ‘stop that’ at me in front of other customers. The forecourt was packed and it was quite embarrassing.

“She told me that they had CCTV and that they intended to report me to police for breaking the law and that I was only allowed to fill up two containers.

“When I got home I did some quick research and discovered that there is no law about how many containers you are allowed to fill.”

Mr Cupis said he contacted Tesco via Twitter and asked which article of law they were using to back up their policy on the number of fuel cans that can be filled.

He said he was told that a “maximum of two containers" for the carrying of fuel is allowed by law under the Carriage of Dangerous Goods and the European Agreement Regulations.

But Mr Cupis said he believed that was incorrect.

"Why are they threatening to report people to the police with a law that doesn’t exist?" he said.