New research from Ofcom has shown that the leading internet service providers (ISPs) - including BT, TalkTalk and Sky - are offering customers download speeds far lower than their advertised headline rates.
The Ofcom study looked at 11 broadband bundles on offer from seven of the UK's largest ISPs.
In the 'up to 8Mb' category, Ofcom found that download speeds were often half the advertised rate - particularly between 20:00 and 22:00 on weekdays - the most popular surfing time.
BT's 8Mb package averaged between 4.1 and 4.8Mb, Orange clocked up between 3.3 and 4.3Mb, while Plusnet racked up just 3.4 to 4.4Mb.
Surfers signed up to broadband bundles offering 'up to 20Mb' or 'up to 24Mb' fared even worse.
BT's 20Mb package had average download speeds of between 6.9 and 8.7Mb, Sky's equivalent broadband deal offered download rates of between 7.4 and 8.8Mb, while TalkTalk managed between 7.7 to 9.3Mb for its 'up to 24Mb' service.
Ofcom claimed that while the sample size was small and duration of the study was short, they believe the results would be similar in 95 out of 100 cases.
The broadband deals in which real world rates most closely matched headline rates were those using fibre optic technology. With BT's 'up to 40Mb' bundle averaging 30.5 to 33.1Mb and Virgin Media's 'up to 50Mb' broadband deal averaging between 43.9 and 47.2Mb.