The UK’s regulator said it had reason to suspect that Plusnet, a subsidiary of BT, may have failed to comply with requirements to give customers clear information.
Ofcom said: “We have since received information giving us reason to suspect that Plusnet – another BT subsidiary – may also have failed to comply with these requirements.
“As a result, our investigation will now consider if BT has breached Ofcom’s rules because of suspected breaches by each of these subsidiaries.
“We will gather further information and provide updates as our investigation progresses.”
In October, Ofcom opened an investigation into EE after discovering that the mobile operator, owned by BT, my have also failed to comply with requirements.
The summary required of providers must include information about price, length of contract and the terms and conditions if a customer decides to end their contract early.
