Roadside cameras recorded number plates before flashing their registration on to screens and revealing the grade of oil recommended for use in the car’s engine.

Castrol used another firm to obtain the data, which is believed to have contained most of the 34million-strong driver details held by the DVLA.

This identified the make, year, engine size and model of vehicle, enabling Castrol to specify the lubricant suitable for each car.

Liberal Democrat transport spokesman Norman Baker said: ‘This completely inappropriate and unacceptable behaviour by the DVLA shows how cavalier it is with motorists’ information.

‘They don’t even check what the end use is. It seems all you have to do is ask and the DVLA will give, no matter who you are and for what purpose. It’s outrageous this was allowed to happen.’

This is a little creepy.