BLUNDERING police staff racked up a repair bill of more than £20,000 in the past two years by putting petrol in diesel-powered vehicles.

Figures released by Essex Police show employees filled up with the wrong fuel on more than 100 occasions since 2008.

The errors continued despite the force spending £4,000 on “talking” fuel caps two years ago to remind staff what sort of vehicle they were driving.

A police spokeswoman said: “We are constantly reminding staff to ensure they use the correct fuel.

“However, our staff drive both petrol and diesel vehicles during the course of their work and unfortunately mistakes happen. We have around 900 vehicles and do fit devices to prevent wrong fuelling. This is not a concern unique to the police service and is a problem nationally.”

Pumping petrol into a diesel vehicle can reduce lubrication and severely damage the engine.

Depending on how far the petrol goes into the system, it can be cheaper to replace the engine rather than try to fix it. Repairs bills can be up to £5,000.

In 2008, police revealed they spent £42,000 during the previous five years because staff had misfuelled 222 times. In an effort to curb the number of mistakes, chiefs bought large, yellow fuel flaps to act as a reminder and several light-activated voice reminders, which chirped “This is a diesel vehicle”.

Despite these measures, staff repeated the error 54 times in 2008/09 and 56 times in 2009/10. It means that out of the force’s 715 diesel vehicles, one in thirteen were misfuelled every 12 months.

Officials said there was a big decrease in the number of mistakes between April and December last year.

A spokesman for breakdown company RAC said: “We estimate someone will misfuel their vehicle every three-and-a-half minutes. It’s a simple, but costly error.”