One in eight vehicles has at least one illegal and potentially dangerous tyre, according to data from car care company motoreasy.

Based on more than 1,000 tyre inspections at motoreasy approved independent garages across the UK, a further 24% of tyres had tread so close to the legal requirement, a replacement would be imminent.

Londoners are the worst offenders, with one in five tyres below the legal limit. In contrast, motorists in Scotland have the highest pass rate with only 6% of cars needing a replacement tyre.

The tread depth must be at least 1.6mm across the central three-quarters of the breadth of the tyre. This also applies to the spare tyre, yet 17% of those inspected were illegal, or would be, following a short usage.

"Based on these figures, that’s over three million motorists breaking the law. And those driving with badly worn or defective tyres are increasing the chances of being involved in an accident," says motoreasy managing director David Gerrans.

National and regional averages – taken from network of motoreasy approved garages:

Region Illegal tyre Almost illegal Illegal spare
London 20% 32% 25%
Wales 17% 28% 13%
South East 15% 27% 22%
Central 13% 27% 14%
North West 11% 22% 16%
North East 8% 25% 18%
South West 7% 16% 16%
Scotland 6% 14% 12%
National average 12% 24% 17%