The UK’s biggest internet provider reported outages in several areas at around 9.30am.
A spokesman said the problems appeared to be mainly affecting London and the South East - but the website Down Detector has already received thousands of reports from the capital, Birmingham, Manchester, Sheffield, Liverpool, Milton Keynes, Leeds, Bristol, Nottingham and Leicester.
BT’s customer support Twitter account said it was attempting to restore service as quickly as possible.
The company said: “Some BT Broadband customers have reported problems accessing websites this morning. Sorry, we’re aware of a problem & working to fix asap.”
The outage comes a day after MPs warned that BT must “put its house in order” or face a break-up after failing to invest in its Openreach network arm potentially to the tune of hundreds of millions of pounds a year.
The outage comes just a day after the telecoms giant was warned to improve service at its Openreach broadband network arm or face a break-up of the company.