Setting insurance premiums on the basis of differences between men and women has been ruled to be discriminatory by the European Court of Justice.
The judgment means that women drivers could face a rise in car insurance rates, with a fall in rates for men.
The court ruled that using differences between men and women as a risk factor in setting premiums breaches European Union rules on equality.
It said: 'Taking the gender of the insured individual into account as a risk factor in insurance contracts constitutes discrimination.'
The verdict will apply from 21 December 2012.
It will force changes in the current standard practice across Europe of basing insurance rates on statistics about differing life expectancies or road accident records of the sexes.
Until now, discrimination in setting insurance rates has been explicitly permitted under EU equal treatment rules 'if sex is a determining risk factor ... substantiated by relevant and accurate actuarial and statistical data'.
But today the judges followed advice from the court's Advocate-General that 'higher-ranking' equality provisions set out in the Charter of Fundamental Rights of the Lisbon Treaty must now apply.
The December 2012 deadline will give insurance companies and risk assessors time to change the template for risk assessment.
Conor Faughnan of AA Roadwatch said the ruling was a triumph of equality over fairness
Mr Faughnan said it would result in the systematic overcharging of young women to subsidise male drivers.
Policy Director of the Irish Association of Pension Funds Jerry Moriarty said all pensions will cost more, but particularly for men, because of the court's ruling.
