Consumer group Which? has reported that 15 million UK homes do not get the internet speeds they pay for, and that there is a large divide between urban and rural areas.
Which? said that a "staggering" 74 percent of households do not get the connections that they signed up to, and that just 17 percent get close to the speeds advertised by their provider.
The situation is better in cities and other urban areas, where 30 percent get the promised speeds. This compares with just one percent in rural areas.
Up to three-quarters of UK households are still not getting the top broadband speeds promised by advertisements - Which research @WhichUK— Chris Choi (@Chrisitv) June 18, 2015
Advertised and actual broadband speeds are often the source of controversy, and are regularly presided over by the UK Advertising Standards Authority.
Which? said that it has already spoken to the advertising authorities about the figures, and that it will now raise the concerns with telecoms watchdog Ofcom, where perhaps more concrete action could be taken.
Advertising guidelines dictate that 10 percent of customers should get the maximum advertised speeds, but many of the big-name ISPs do not come close, according to Which?. For example, just one percent of BT 76Mbps customers get what they pay for.
"It's not good enough that millions of homes are so poorly served by their broadband provider with speeds that just don't live up to what was advertised," said Which? executive director Richard Lloyd.
"Broadband is an essential part of life these days, so people shouldn't be persuaded to buy a package which is never going to live up to expectations.
"We've raised our concerns with the advertising authorities, but we now want Ofcom to ensure that consumers get the speeds promised by providers."
BT told V3 that the company follows official guidelines in marketing its services, and advises customers that they may not get the fastest speeds.
"We're very clear that customers should not rely on headline claims, but instead use the personal speed quote we give them at the point of sale, which is based on their own line," said a spokesperson.
"If they aren't happy with this personalised speed they can decide not to buy from us. If they are happy with the speed, but find they don't achieve it, we allow them to end their contracts in line with the Ofcom code of practice."
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