UK broadband users are paying for vastly exaggerated internet speeds, with an average 7 megabits per second (Mbps) compared to their providers’ promised 12Mbps – five megabits lost between the claim and the actual usage.

A Guardian online survey of 3,000 readers found most users paying for better broadband access than they actually receive.

The worst-performing ISPs were Sky and TalkTalk, where users reported a 60 percent shortfall between what these broadband providers advertised and what users actually experienced.

Sky subscribers bought into advertised broadband speed rates averaging 12Mbps but received a mere 4.8Mbps.

TalkTalk customers were promised an average 8Mbps speed, but reported just 5Mbps.

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Virgin subscribers fared better but the gap between advertised and actual rates were still 41 percent apart – getting 17.7Mbps instead of the promised 30Mbps.

Much maligned former public telecoms provider BT came out on top of the satisfaction charts, with a sizeable but below-average shortfall of 27 percent on BT’s well-respected PlusNet service.

Ofcom defines “broadband” as 2Mbps or over, which is the minimum bandwidth needed for video services such as the BBC's iPlayer.

18 percent of Guardian survey respondents reported that their so-called broadband lines were under this measure.

Last week BT announced the passing of the 10 million Infinity broadband milestone, and also a long list of new UK exchanges that can handle the fast Internet access.

The 80Mbps fibre-to-the-cabinet (FTTC) technology roll out is “months ahead of schedule” according to the telecoms giant.

Even faster 300Mbps fibre-to-the-premises (FTTP) broadband is promised from spring 2013.

80Mbps BT broadband available for 10m in UK

BT also announced a long list of new fibre-broadband ready exchanges.