Thousands of UK motorists are thought to have lost millions of pounds in an international card-skimming scam believed to have funded a Sri Lankan terrorist group.

Police think that the cards are being cloned at petrol stations across the country, with card details and PIN numbers being pinched and money withdrawn from customer accounts.

The Sri Lankan government has accused a criminal gang of carrying out the skimming campaign to fund attacks by the Tamil Tigers separatist group.

Maxwell Keegal, first secretary of the Sri Lankan High Commission in London, said that the government there had evidence to suggest that the militant group has been assisting Sri Lankan criminals to work in petrol stations and then forcing them to commit fraud. The UK authorities are investigating the claims but say there is no confirmed link.

Police began investigating when they received thousands of complaints from drivers in Leeds, Bristol, Hull, Nottingham, Norwich, Edinburgh and Peterborough. Around 200 petrol stations are thought to have been hit by the criminals.

“We are working very closely with the [British] police,” said Keegal. “The Tamil Tigers are behind this and I would urge the British authorities to crack down on it now. It will only get worse and more widespread if the network of ringleaders is not targeted.”

Ray Holloway, director of the Petrol Retailers Association, said that his organisation had tried to halt the fraud by training staff and checking equipment in the petrol shops. But added: “Criminal gangs that are involved in this offer quite large sums of money to some employees in order to actually take part in it.”