An unnamed peering network has been blamed for causing buffering problems for Virgin Media customers at peak times.
In recent weeks, a number of the broadband provider's subscribers have complained about problems streaming online video.
One customer told the Register that access to YouTube, iPlayer, and other streaming sites "has been getting steadily worse".
Speaking to the news provider, a Virgin Media spokesperson stated: "As a result of an issue with a third-party peering network, some customers have been having trouble accessing certain websites and online services even though their broadband speeds are unaffected.
"We began re-routing traffic towards the end of last week which has had a positive effect."
The spokesperson said Virgin Media is working to resolve the issue as soon as possible.