BT has been accused by the BBC of capping bandwidth for content-rich video services.
According to BBC news, the operator limits download speeds at peak hours for customers using platforms such as its own iPlayer and the website YouTube.
It claims that customers with an 8Mb package can expect to see their connection scaled back to below 1Mb at busier times of the day.
The broadcaster said in a statement: "We are concerned that at peak times some customers' higher quality video streams may be interrupted by buffering before falling back to a lower-quality version."
It added that this suggests iPlayer traffic is "being throttled back" and bandwidth is being limited on slower connections.
In response, BT stated that it was currently in discussions with the BBC to ensure customers "get the best possible experience".
BT is currently the UK's most popular internet service provider, with approximately 4.8 million customers.