Ofcom's report into fixed-line broadband speeds has been dismissed by internet service provider BT as being "sadly out of date".
The telecom regulator conducted speed tests with technology company SamKnows over 18 months to find that BT customers on 8Mb broadband deals typically receive download speeds of 3.8 to 4.2Mb.
According to the study, BT customers trailed those with Orange, O2 and Virgin Media, among others.
However, BT's consumer managing director John Petter said that the figures for the ISP are inaccurate because it has already started moving customers onto its 21st Century Network (21CN).
"In addition, we are making exciting progress in our trial for fibre to the cabinet - which will offer speeds far in excess of what Virgin Media offers most of its customers today," he added.
Mr Petter also questioned the methodology of the study, suggesting that it penalised BT for providing broadband services in areas that other ISPs avoid.
Meanwhile, BT Openzone announced this month that it has set up Wi-Fi hotspots at six of Flybe's UK lounges.