Broadband users are not getting the speeds they are paying for, according to the largest survey of its kind ever undertaken by telecoms regulator Ofcom.

电信运营商Ofcom开展的最大的一项调查显示，宽带用户实际使用带宽与没有达到之前付款的要求。

Nearly one fifth of UK broadband customers on an 8 Megabit per second (Mbps) connection actually receive less than 2 Mbps, it found.

The research showed that less than 9% of users received more than 6 Mbps.

However, the report shows that average connection speed across the UK is 4.1 Mbps, up from 3.6 Mbps in January.

"It's very easy to go out and find out what the price of broadband is, but much more difficult to get a good understanding of what the observed speeds are likely to be," said Ofcom chief executive Ed Richards.

The report also ranked the average speeds of nine major UK ISPs, with Virgin¹ Media coming out on top.

'Slow lane'

In order to address the issue of speed, Ofcom worked with Samknows, a broadband measurement firm that specially² modified the routers（路由器） that decode³ the signal coming into subscribers' homes.

While many websites offer speed tests, their results can vary widely due to a number of factors aside from the ISP's speed; the routers measure the ISP's delivered speed regardless of these factors.

The routers collected speed data from 1600 users' connections nationwide between November 2008 and April of this year - amounting to some 60 million separate speed tests in all.

The numbers were then adjusted for a given user's distance from the telephone exchange. For broadband that comes through traditional copper⁴ wires, such as ADSL, the measured speed is lower for users who are farther from one of the country's 5,800 exchanges.

The speed study was accompanied by a survey of subscribers（捐款人）, finding that although more than 80% were satisfied overall with their service, about a quarter said the network speed was not as fast as they had expected.

Because the measured speeds varied⁵ so much, a simple league table of ISP speeds is difficult to make.

However, Ofcom released a table which shows comparisons for nine major ISPs, showing which are faster and slower.

"The Ofcom study is important as it quantifies accurately⁶ for the first time what consumers have known for a long while - namely that you are extremely unlikely to receive the advertised broadband speed," said Charlie Ponsonby, chief executive of broadband comparison site Simplifydigital.

"Also for the first time it makes a robust⁷（强壮的，强健的）, like-for-like comparison between broadband providers."

However, BT, who ranked lower in the survey, criticised the report.

It said the sample size was too small and the results were "unreliable".

In particular, it said that because it provided rural broadband its average speed was bound to be slower than other ISPs.

"We have many customers whose lines are at the limit of broadband service, with resulting lower average speeds," it said in a statement.