"About 300,000 motorists have crashed because of a satnav, the Mirror has found.
Around 1.5 million drivers have suddenly veered dangerously or illegally in busy traffic while following its directions.
And five million have been sent the wrong way down a one-way street.
Katie Shephard of safety charity Brake warned lives were in danger and said: "Anyone buying a satnav must consider whether they can be safe on the road."
Campaigners fear many of the the 14 million users put lives in peril by slavishly following their instructions and also neglecting road safety.
One in 10 drivers with a satnav says following its instructions made them take a dangerous or illegal turn.
Twice as many blame the gadget for making them hesitate on a busy road and lose track of road traffic.
More than one in 50 - almost 300,000 drivers - say it has caused or nearly caused an accident.
Maggie Game of insurance giant Direct Line, which carried out the survey for the Mirror, warned: "If a satnav gives you an instruction that is likely to endanger other road users, ignore it.
"Motorists must realise that while they are a helpful navigation tool, they should not follow their instructions to the detriment of road safety." (Continued via Usability News, mirror.co.uk) [Ergonomics Resources]