By Jonathan Davies

Communications regulator Ofcom is investigating Sky over claims that it does not allow customers to cancel their subscription at the end of their contracts.

Ofcom said its investigation, which is expected to last well into next year, will look at whether or not it breached its obligation to customers to provide a good cancellation service.

Under Ofcom's rules, the process must not dissuade customers to change provider.

Ofcom said: "Ofcom's investigation will examine whether there are reasonable grounds for believing that Sky has failed to comply with [its] obligations."

At the start of January 2014, the Telegraph exposed problems people experienced cancelling their contracts.

Sky, like many other TV, phone and broadband providers, enforce minimum contracts, meaning you'd have to pay the remainder of the contract if you decided to leave early. Once the minimum term has ended, however, you are free to leave whenever you want. Or so you should.

Sky says that customers can cancel their subscription via phone, fax, email or letter. According to the Telegraph's investigation, a number of those who wrote to Sky did not have their accounts closed. In fact, Sky said it would only accept a cancellation if it was "verified" over the phone.

In May 2014, Sky agreed to change its customer agreements, making it clear that customers had to phone in order to cancel their subscription. However, one area of its website said customers could cancel via a live online chat. But further down the page, it also read: "Please note, we won't be able to cancel your services unless we verify your request over the phone."

A Sky spokesman said: "We're committed to delivering the best service in the country and we believe this is one of the reasons why more customers than ever are choosing Sky. We will work closely with Ofcom to help them with their investigation."