Women's car insurance is expected to rise drastically from 21st December after a European Court of Justice (ECJ) ruling on gender equality.

In short, the court has ruled women cannot be charged lower rates for car insurance simply because they are women and the gap in premiums for men and women will now close.

However, this does not mean men's car insurance will drop; instead it means women's car insurance will rise to meet that of the men's from this month.

According to data from leading insurance expert MoneySupermarket.com, the gap between insurance for men and women's car insurance is actually growing bigger.

The average car insurance premium for men between July and September 2012 is £508, a reduction of 10.4 per cent compared to the previous year.

While this may seem like good news for men, the average women's insurance in the same time frame was just £393 and it had decreased at a faster rate (11.3 per cent) than the men's.

Kevin Pratt, insurance expert, said: "In the last Monitor we reported that the cost of car insurance for female drivers was particularly competitive and this is reflected in this data set showing that the gender gap is actually increasing as insurers look to take on female business ahead of the ECJ deadline."

Women drivers are now being urged to shop early for insurance before the changes are implemented or face drastic rises in premiums for next year.

However, some critics of the ruling say women are statistically safer drivers and insurance costs should reflect the difference in gender.

MoneySupermarket.com statistics show women are actually more likely to make an insurance claim but they are usually much smaller claims than those made by men.

It also says men are more likely to choose bigger cars with more powerful engines such as the Ford Mondeo, while women favour smaller cars such as the Ford Ka city car.

Maggie Craig, acting director general of the Association of British Insurers (ABI), said: "This gender ban is disappointing news for UK consumers and something the UK insurance industry has fought against for the last decade.

"The judgment ignores the fact that taking a person's gender into account, where relevant to the risk, enables men and women alike to get a more accurate price for their insurance."

Meanwhile, the AA has calculated up to £400 could be added to the cost of insurance for young women, who already face premiums of up to £2,700 for those who are 18 years old.

The changes will come into affect across the UK, meaning the great gender debate will continue, but women will lose out even if they actually are safer drivers.