More than half of UK internet users are being short-changed when it comes to their broadband speed, according to campaigners trying to bring the providers to task.

A study by vnunet.com's sister title Computeractive, in conjunction with BroadbandChoices and Thinkbroadband.com, found that 62 per cent of broadband users are achieving less than 50 per cent of their advertised speed.

A national survey of the actual performance of Computeractive readers' broadband connections revealed that 62 per cent of users consistently receive less than 50 per cent of the advertised speed to which they signed up.

And a shocking 25 per cent of the 180,000 people who completed the test received only a quarter of their maximum advertised speed.

The three partners have launched the Crystal Clear Broadband campaign to challenge Ofcom and the broadband industry to improve clarity in broadband contracts for UK internet users.

They plan to lobby Ofcom to oblige ISPs to provide clear information about the actual speed customers are likely to receive, much like the 'typical rate' published by credit card and loan providers.

The campaigners want customers to have access to this information before they commit to a contract.

The initiative will also encourage Ofcom to run its own independent speed-testing service so that consumers can compare advertised maximum rates against actual speeds.

"Ofcom currently permits ISPs to advertise only theoretical maximum rates for broadband connections, and most ISPs include the caveat that consumers can only expect speeds 'up to' this maximum," said Computeractive editor Paul Allen.

"No information is available on what consumers can expect in practice, despite providers having access to tests that would give a much clearer idea of potential speeds."

The survey of Computeractive's readership showed that 53 per cent of those questioned were unaware that ISPs are not contractually obliged to provide a minimum service rate.

UK competition minister Stephen Timm, said this week that the UK risks falling behind the rest of Europe if it fails to improve broadband speeds.

"Other countries are starting to invest in new fibre-based infrastructure delivering considerably higher bandwidth than is available in the UK today," he warned.