Which? called upon industry regulator Ofcom to investigate ISPs whose advertised broadband speeds bear little resemblance to what most home users can actually achieve.
The consumer group found an average home broadband connection speed of 2.7Mbps, in one case dipping as low as 0.09Mbps.
Which? also found low levels of consumer satisfaction with broadband giants. Only 30 per cent of customers said they were "satisfied" with their ISP, with Orange, Bulldog and Tiscali among those most poorly rated.
Smaller providers fared better, with Waitrose and Zen Internet scoring more than 70 per cent on customer satisfaction.
Which.co.uk editor Malcolm Coles appealed to Ofcom and Trading Standards to ensure that ISPs weren't taking advantage of consumers.
Coles said in a statement: "It’s shocking that internet service providers can advertise ever-increasing speeds that seem to bear little resemblance to what most people can achieve in reality.
If it’s unlikely you’ll reach the advertised speed, it should be made clear up front, so that you know with some certainty what you’re buying."
In response, Ofcom said it was working closely with the Advertising Standards Authority(ASA) and would monitor any increase in the level of complaints received from broadband consumers.
Last year the ASA ruled that ISPs could only claim speeds of "up to 8Mbps" if a "significant proportion" of customers could achieve that speed.
Bulldog was forced to withdraw adverts for "up to 8Mbps" broadband after an ASA ruling last September.
Which? tested connection speeds of 27 ISPs in more than 300 households. Researchers also surveyed 14,642 members of the public about ISP customer service.
Advertised broadband not up to speed, says UK watchdog
By Jane Hoskyn on Aug 6, 2007 11:13AM