Male motorists typically pay £101 more a year for their car insurance than women, a comparison site has suggested.
Men paid an average annual premium of £812 for comprehensive car insurance in the final quarter of 2016 compared with £711 for women, according to Confused.com.
Its research suggested that the gap had widened compared with a year earlier.
Insurers are banned from considering gender when setting premiums but can consider wider risks.
Amanda Stretton, of Confused.com, said that insurers were "becoming more astute" in identifying particular accident risks, and would price premiums accordingly.
She said that, in general, men drove more miles, in more advanced cars, and were more likely to drive for work - all of which would increase the probability of accidents or increase the repair bill.
European rules, introduced at the end of 2012, mean insurers cannot take the gender of their customers into account when setting their insurance premiums.
Other factors can be considered but, after the new rules were introduced, men only paid £27 more on average on an annual premium, Confused.com calculated.
This widened to £51 two years ago, before going above £100 for the first time in the final quarter of last year.
In general, the typical comprehensive car insurance premium stood at £767, rising by 14% - or £95 - in a year, it said.
James Dalton, director of general insurance policy at the Association of British Insurers (ABI), said: "Motor insurance remains a highly competitive market, with motorists shopping around for the best deals. But pressure is growing on premiums.
"Cold callers and ambulance-chasing lawyers are still finding ways to exploit the system, with government data suggesting a 5% increase in whiplash style claims. This is driving up costs for honest motorists.
"In addition, the government has doubled Insurance Premium Tax in just over a year, and repair bills are going up as cars get more sophisticated. So while insurers are doing all they can to control costs, these pressures show how important it is that the government's latest proposals to tackle low value whiplash style claims are implemented fully and as quickly as possible, and that there is no rise in Insurance Premium Tax."