Broadband speeds drop by as much as 40 per cent during peak times, a report has concluded.
Tests by Broadband.co.uk showed that the difference between Tiscali's best and worst speeds were just under 40 per cent last month, with the average drop around 25 per cent.
At the other end of the scale, O2 and Be Broadband, which are marketed as separate brands but use the same unbundled network, have a difference of only 11 per cent.
"When comparing download speeds for all providers between various times of day, we can see that the average speed drops by over a quarter at peak times showing work still needs to be done to increase capacity to meet demand," said Edd Dawson of Broadband.co.uk.
However, the report, which was compiled using information from speed tests carried out by surfers on the Broadband.co.uk website, showed that the average speed of broadband lines in the UK had increased.
"The average speed nationwide has increased for the first time since July 2008, up by 14.02 per cent to 3.667Mbps," Dawson said.
Virgin Media was named the fastest broadband provider for the fourth consecutive month. The company recently launched 50Mbps broadband in selected areas of the country.