It said the “galloping inflation” of premiums meant there was an urgent need for clients to be able to cancel policies at any time.
Researchers from UFC Que Choisir analysed 500 different contracts from 86 companies and found “massive” rises.
The median rise – halfway from highest to lowest – for one company was 12%. Half the contracts showed rises of more than 5%, when average inflation is 1.1%.
Que Choisir also criticised the “huge variation in charges” between companies which “all work in the same market conditions”.
Some, such as Macif, raised premiums by just 2.7%.
The 5% average rise for 2020 was more than the 4% in 2019. It coincides with the start of the new 100% Santé policy that improves reimbursements for some optical and dental care, which the government said would have “no effect” on mutuelle premiums.
Mathieu Escot, of UFC Que Choisir, said: “Parliament voted a law last year to allow customers to cancel contracts at any point, but it has still not come into effect.
“It is due by December 1 this year, but we have asked the new health minister to bring it into force sooner so customers can get value.”
Que Choisir internet subscribers (€45/year or €6.99/month) can use an online mutuelle checker at tinyurl.com/glno7xc.