New European rules have come into force, which mean insurers will not be able to charge different rates based on gender.
Traditionally women have had lower car insurance premiums because they are statistically less likely to have accidents than men.
Today's move follows a March 2011 European Court of Justice ruling outlawing insurers from charging men and women different prices on grounds of sex discrimination.
The move will likely lead to higher insurance costs for consumers, particularly for women drivers below the age of 25.
It has drawn criticism from insurers who say gender exerts a strong influence over how likely a person is to claim, and should be reflected in the premiums they pay.
Insurers could try to sidestep the ban by basing their pricing on proxy gender indicators such as the customer's profession or model of car, although this would be vulnerable to legal challenges, law firm Eversheds said.
The ban was also expected to boost demand for so-called telematics insurance, where insurers monitor customers' behaviour through devices installed in cars, and charge according to how riskily they drive, irrespective of gender.