Broadband, TV, mobile and home phone companies will have to tell customers when their contract is coming to an end and show them the best deals available under new rules unveiled by Ofcom.

The telecoms regulator said the move, the latest in its Fairness for customers programme, could see up to 20 million customers benefit by switching provider or agreeing a new deal with their existing one.

Ofcom said people who bundle their landline and broadband services together pay on average around 20% more when they are out of contract and this rises to 26% among customers who bundle in their pay-TV services.

It said that around one in seven customers do not know whether they are still tied to the original deal.

Ofcom's consumer group director Lindsey Fussell said: "We're making sure customers are treated fairly, by making companies give them the information they need, when they need it.

"This will put power in the hands of millions of people who're paying more than necessary when they're no longer tied to a contract."

The changes will involve providers sending tailored information to millions of individual customers, including the contract end date, the price before this date, any proposed changes and the best deals offered by their provider.