As of 1 April 2017, general insurers must clearly display last year’s premium in renewal notices as well as the proposed premium for the year ahead.

This is so customers can see exactly what they paid and encourages them to shop around for the best insurance cover and price.

But a sample review by regulator, the Financial Conduct Authority, to see how firms were implementing the new rule revealed that Aviva’s notices weren’t up to scratch.

Aviva failed to prominently display last year’s premium and its messaging encouraging customers to shop around should have been clearer.

As a result, the insurer is writing to affected customers to provide them with the information in the correct format. However, it is not disclosing how many customers have been affected.

While premiums provided were correct, if customers feel their decision to renew would have been different based on receiving the full information, Aviva said they should contact it to discuss the matter.

A spokesperson added: “Following a review, we are aware that we have not interpreted all the renewal transparency rules in the way they were intended for some customers. We have amended our processes to ensure they meet the requirements going forward.

“Although premiums provided to customers were correct, we are contacting any customers who may have been impacted to apologise and provide the required information again in the correct format. We are committed to transparency around our pricing and giving our customers clear information, so they can make the right choice for their insurance cover.”