Four million cars could be being driven illegally with tyres below the limit, new research conducted by vehicle repair company Halfords Autocentre has found.

The poll of 2,000 motorists uncovered that 13 per cent have knowingly driven with bald tyres.

Furthermore, almost two-thirds admitted not fully understanding the rules surrounding driving with worn out tyres – doing this could result in a dangerous blowout or a fine from the authorities.

In addition, 65 per cent claimed they didn’t know the legal tyre depth of 1.6mm across the central three quarters of the tyre. Motorists risk a £2,500 fine and three penalty points per tyre if caught, resulting in a £10,000 fine and a loss of licence if all four tyres aren’t within the legal limit.

The survey also found that 27 per cent of drivers have failed to check their tyres in the past three months, while 42 per cent were unaware of how to check their tyre pressures.

Martin Barber, Halfords Autocentres tyres expert, said: “We were surprised to find that so many Brits are driving below the legal tread depth, which can reduce braking and steering ability especially in unpredictable weather and wet driving conditions.”