The Ofcom Consumer Panel, one of the independent regulator's main advisory bodies, has written to Britain's largest internet service providers (ISPs) urging them to be more up-front about connection speeds.

In its letter, the panel said that broadband selling practices had to change so that consumers were made more aware that the speed they can actually expect to receive will rarely match up to the advertised level.

Recent research from consumer group Which? found that products advertised as 8Mbps were on average clocking up mere 2.7Mbps connections.

A variety of factors can influence the speeds of an ADSL broadband connection, including the distance between the customer and their telephone exchange, the quality of locally installed copper lines and usage levels on local grids.

But while the Ofcom panel accepted that such variations were unavoidable, it said the burden fell on broadband providers to give their customers realistic expectations - with reliable high-speed connectivity an absolute must for anyone looking to use VoIP telephony and other bandwidth-heavy services.

The advisory body also recommended providers extend their cooling-off periods, during which time new subscribers have the option of cancelling their contract if they are dissatisfied with the service.