The communication regulator, Ofcom, said it is investigating whether Shell Energy issued broadband and landline customers best tariff notifications when they were coming to the end of their contracts.

In February 2020, Ofcom introduced rules requiring broadband, mobile, home phone and pay-TV companies to warn customers when their minimum contract period is coming to an end, and what they could save by signing up to a new deal.

The firms are also required to remind customers who are out of contract about their best deals every year.

Ofcom said information provided by Shell Energy “indicated that it did not send these notifications to some customers for a period of time starting in February 2021”.

In other letters sent to customers, they may not have set out all the required information.

Ofcom said it aims to complete the investigation by the end of summer 2022, and will publish an update then.

An Ofcom spokesperson, said: “These notifications play a vital role in helping people save money. More than a million broadband customers have secured a better deal since their introduction, but millions more are still out of contract and paying more than they need to. We’re investigating whether Shell Energy is meeting its obligations to send customers these important alerts.”

A Shell Energy broadband spokesperson, said: “We take our customer responsibilities very seriously which is why we alerted Ofcom to an issue where we did not send communications to some of our customers regarding the end of their contract, although the price they paid was unchanged.

“We’ve since addressed the issue and sent appropriate reminders to the affected customers. We look forward to working with Ofcom to outline the improvements we’ve made and assure them of our commitment to delivering an excellent customer experience.”