Only one in 25 people subscribing to broadband services claiming data rates of 'up to' 16Mbits/sec get the full rated speed, according to a new survey.

The Point Topic survey of Britain's top six service providers shows that lower your rated speed, the more likely you are to get it.

Just over seven in ten people with 512Mbit lines reported getting full speeds, with the figure trailing off to 23 percent at 4Mbit, 15 percent at 8Mbit and 4 percent at 16Mbits.

“There are many variables that affect broadband speeds, distance from the exchange, contention, line quality and so on.It is a challenge to be able to factor all these into a calculation that gives you a reliable idea of the actual speed an individual connection will achieve,” says Point Topic research analyst Pam Varley.

Four thousand users were questioned by YouGov on behalf of Point Topic. The results show that you have a fair chance of getting speeds of above 2Mbits/sec if you subscribe a service advertised as capable of this, even if you don't get your full rated speed,.

The percentages of people in this category reporting speeds above 2Mbits/sec were: Sky, 79, Virgin Media 76, Tiscali 72, Carphone Warehouse 66, BT 65 and Orange 63.

That still leaves between 21 percent and 37 percent of people paying for high-speed access who can't hit faster than 2Mbits/sec.

The findings are broadly in line with those a a survery conducted last year by our sister magazine ComputerActive.