The telecoms giant said on Monday afternoon that it is trying to fix a major issue which has impacted its broadband, 4G and 5G services.
More than 100,000 customers highlighted issues with the services on Monday, according to monitoring website DownDetector.
Customers first reported problems after 2pm, with most highlighting that their home internet service was down.
A smaller number also said that they could not access the internet through their mobile phones.
A spokeswoman for the company said: “We are aware of a major issue on our network currently affecting broadband, 4G and 5G services.
“We appreciate our customers’ patience while we work to resolve this as soon as possible.”
Customers also had issues accessing the company’s own website, which was knocked by the outage.
The telecoms firm has more than 18 million customers in the UK, including around 700,000 home broadband customers.
Users of the Voxi mobile operator, which is also owned by Vodafone, also reported issues about its service.
