The European Commission is taking the UK to court “for not properly applying the rules” on red diesel.

Agricultural vehicles and fishing vessels use diesel which is dyed red to show they pay a reduced tax rate. It can be up to 40% cheaper than diesel typically sold at petrol stations.

However, many private yachts are using it and avoiding the higher duty.

The Commission stated: “Currently, UK law does not require fuel distributors to have two separate fuel tanks to distinguish between the lower tax marked fuel and the fuel subject to the standard rate. As a result private leisure boat owners are often in a situation where they can only purchase marked fuel.

“As a consequence, private leisure boats may not pay the right amount of tax as they purchase use fuel normally intended for fishing vessels.”

It also puts private leisure boats at risk of heavy penalties if they are checked by local authorities when they travel to another member state, the Commission added.