Nearly 90% of the garages investigated by Which? missed or ignored at least one potentially dangerous fault, while 39% charged for a product that wasn’t supplied.

The consumer watchdog introduced four deliberate faults – deflated spare and nearside rear tyres, brake fluid at the minimum level and a blown bulb on the reversing light.

However, just eight of the 62 garages tested returned the cars fault-free, while five garages failed to fix any of the faults.

“This is a worrying snapshot of an industry that desperately needs to clean up its act,” said Peter Vicary-Smith, chief executive of Which? “Almost all the garages in our investigation failed to fix basic faults.”

Nearly half (48%) didn’t spot that the brake fluid was at the minimum level, 68% didn’t inflate the flat spare tyre, 57% missed the blown reversing light bulb and 21% didn’t notice the low pressure in the nearside rear tyre.

The screenwash was also filled up as an honesty test to see how many garages charged for it anyway - 39% did so.

“Surveys like this show why more and more businesses are using fleet management services for their vehicles,” said BVRLA chief executive John Lewis.

“As well as having a wealth of technical expertise, these providers have also established robust service level agreements with a range of garages and repair shops, which should prevent any maintenance mishaps.”

More follows on page two...