Communications watchdog Ofcom has released data that shows millions of broadband customers are being sold fast connections that internet providers are not able to deliver.
The report, published on Wednesday, says that Britons get an average broadband speed of 6.2 megabits per second (Mbps), which is less than half the average advertised speed of 13.8Mb.
Virgin Media was the only internet service provider that Ofcom found delivered anything like the maximum speed advertised.
The Advertising Standards Authority's committee of advertising practise (BCAP) are carrying out a consultation into how broadband speeds are advertised and are expected to report back in the next three months.
Ofcom have said that internet providers such as Sky, O2 and BT must change the wording of their adverts where promise "up to" broadband speeds that most customers are not able to receive because current infrastructure cannot support these maximum speeds.
Instead, Ofcom believes broadband speeds should be advertised on the speed which customers can expect to receive - a "typical speeds range" - and maximum speeds should only be advertised if they can actually be delivered to a significant number of customers.
Wednesday's report is based on performance tests carried out in 1,700 homes across the UK in November and December 2010, it spans 11 broadband packages from the UK's seven largest providers.
The report also shows that the overall average broadband speed increased from 5.2Mbps in May 2010 to 5.2Mbps in December.