Ofcom has revealed it will once again be testing fixed-line broadband speeds.

Last year, the watchdog tested 1,600 different internet connections in the UK and discovered that actual speeds are considerably lower than the 'headline' speeds advertised by most ISPs.

The research formed the basis of the Ofcom UK Broadband Speeds 2009 report, which revealed that more than 50 percent of ADSL broadband users in the UK can only achieve half the download speeds promoted in ISPs' 'up to 8Mbps' adverts.

The report also said the highest download speed someone with an 8Mbps package can achieve was 7.2Mbps.

The organisation is now calling for web users to sign up to take part in the research, which is being conducted by the Sam Knows website.

The website developed a "white box" that connects to a router to measure broadband speeds.

"Our consumer research has shown that speeds are the single biggest cause of dissatisfaction in relation to broadband," said Ofcom.