Detection teams will dip cars in supermarket car parks and petrol stations in a bid to catch motorists running on red and green diesel.

The UK-wide operation is being launched because a test run by Revenue and Customs recently found that one in five diesel cars was running on illegal fuels.

The crackdown follows a recent rise in duty that pushed diesel close to or over £1 a litre.

That rise could make the cut price red and green varieties - which are designated for use in tractors, diggers and central heating - more tempting to motorists.

The price difference between clear diesel and the red and white varieties can be as much as 65p a litre.

Green diesel is the Republic's version of the red fuel, and is also illegal for use in Northern Ireland.

Colin McAllister, the national oils strategy manager for HM Revenue and Customs, said £350m of Government revenue is lost every year through illegal diesel use, making it "a serious issue nationally".

"We are warning motorists using illegal diesel that the chances of being caught are now greater than ever, and that they risk penalties or seizure of their vehicle when they are caught out," he said.

Businesses caught using red or green diesel could also have their accounts audited for fraud detection.

"During these nationwide operations we will give information to every motorist challenged to raise their awareness of the impact of the unlawful use of red diesel," Mr McAllister said.

"We will also remind retailers of their obligations in relation to the control and sale of red diesel on their premises.

"Those using rebated fuels illegally are abusing a tax system, which is there to support and reduce the burden on UK industries such as agriculture. It isn't about cheating the Government out of a few pounds; it's about depriving our public services of vital funding.

"The exercise next week, and those that will follow, demonstrates how much effort HMRC puts into its oils fraud activities. We want honest fuel retailers to be able to operate without the threat of unfair competition, and we want drivers to be aware of their responsibilities."

HMRC advises motorists to "avoid fuel being sold at noticeably lower prices than the current market rate".

"If the price looks to be too good to be true, it generally is," a spokesman said.