BT says its broadband infrastructure has plenty of "headroom" to cope with increased demand as more people stay home due to coronavirus.
The company said that since Tuesday, data use on its network had increased by between 35-60%.
On Thursday, Netflix said it would lower the picture quality of movies in Europe, to reduce data use.
But BT said daytime and evening usage was still much lower than the highest levels it had ever recorded.
In a statement, BT said: "The additional load... is well within manageable limits and we have plenty of headroom for it to grow still further".
The highest rate of traffic BT has ever seen on its own network is 17.5 terabits per second (Tbps), on an evening where there was high demand for video games downloads and streaming football.
At a data rate of 1Tbps, 125 gigabytes (GB) is downloaded every second - the equivalent of about 55 high-definition movies.
By comparison, average daytime use on BT's network this week has been 7.5Tbps - far below the highest peak that the company said it had been able to handle.
While analysing its data, BT said it discovered that:
- mobile internet use had reduced by 5% on its networks as people stay at home and use the wi-fi
- data use peaked at 17:00 GMT every day this week, the time of Prime Minister Boris Johnson's daily news briefing about the coronavirus
However, it warned that mobile phone voice calls could be affected if demand increased.
It said current use was "well within the levels the network is built to handle", but encouraged customers to use a landline phone if they have one, or internet voice-calling services such as Skype, WhatsApp or Zoom instead.
Virgin Media said it was seeing a similar 50% boost to the amount of downloaded data during the day - but added that this was still below its evening peaks. Uploads, meanwhile, were 80% higher than normal during daytime hours. Virgin said the number of voice calls via its landlines were also up by 80% during the busiest time of the day.
On Thursday, Netflix said it would reduce the bitrate of movies in Europe, to reduce data use by about 25%.
The company said it was in response to "the extraordinary challenges raised by the coronavirus".
Other video-providers are considering similar moves.
Amazon's Prime Video said it was talking to local authorities, and had "already begun the effort to reduce streaming bitrates whilst maintaining a quality streaming experience" in Europe - including the UK.
A spokesman for BBC's iPlayer service said: "We're in contact with the relevant organisations to determine what action to take."
Several factors influence how much data is used when streaming a movie online.
One of them is video resolution, including whether a video is high-definition (HD) or ultra-high definition 4K.
Another is bitrate, which influences how clear and smooth videos look when streamed online
Videos with a higher bitrate tend to look less "blocky" or pixelated, but use more data.
Out of these two, Netflix says it will cut its streaming bitrates. Customers who pay for higher-definition services will still get higher-resolution video.
BT said that Netflix's decision was based on the needs of all European operators - but that the UK's network was resilient.
"The UK has a very capable core network because UK consumers are more heavily invested in HD-streaming video, including live football, Netflix, than many other nations," a spokesman said.
"So in the UK there isn't a pressing need to reduce bitrates at the current time, but we are supportive of the move, as clearly the situation is unprecedented and it is common sense to do it."
With all the extra people working from home, daytime use has only jumped by half, it said, from 5tbps to 7.5tbps.
"I've seen a flurry of media stories reflecting an understandable concern that our networks will be unable to cope with the additional traffic of millions of home-workers," Howard Watson, BT's technology officer, said.
"However the UK's communications infrastructure is well within its capacity limits, and has significant headroom for growth in demand."