The telecoms giant said on Monday it was aware of "intermittent issues" with its services and apologised to customers, adding it was working to solve the issue as a "priority".
In a statement, the company said: "We're aware that some customers are experiencing intermittent issues with their services," a Virgin Media O2 spokesperson said.
Virgin Media is working to fix an issue that has left many customers unable to get online.
More than 9,000 reports of issues have been made since 11am, according to service status website Downdetector, with the majority saying their internet services have been affected.
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