The rules, introduced in April last year, require firms to clearly show the insurance premium a customer paid last year, alongside their proposed renewal premium.

They also order firms to show a “prominent, clear and straightforward” message to encourage customers to shop around.

The FCA said it has found that firms are failing to properly implement the rules despite a warning in October about failings.

Jonathan Davidson, executive director of supervision – retail and authorisations at the FCA, said: “It is simply unacceptable to see that some firms are still not being properly transparent with their customers a year on from the introduction of the rules.  

“Firms failing to get this right may have led to consumers losing out as they do not have the right information to decide whether or not to shop around.

“We have already acted where we have seen particularly poor practice in firms and will continue to do so where we see firms not being transparent.

“As we said in October, we expect other firms to take notice of these issues, to look at what they are doing and to make sure they are getting it right.”