Ofcom has published a voluntary code of practice to govern the way fixed-line ISPs promote and supply their broadband connections.

The regulator is asking ISPs to provide more accurate estimates about the maximum useable speed of the packages they sell, and to allow consumers to change tarrifs when the advertised speed is not reached. It is also asking companies to notify users about the usage limits of the deals they buy.

The move follows widespread criticism of the way ISPs promote their broadband deals. A recent study found that most UK users are only achieving half the access speed promised to them by advertising.

A total of 32 ISPs, covering 90 per cent of the UK's connections between them, have already agreed to adopt the recommendations. Ofcom says it will monitor the compliance of organisations adopting the code, and will consider more formal regulation if its demands are not met.

“Broadband is a thriving market in the UK," said Ofcom chief executive Ed Richards. "We want to encourage real clarity for consumers about the actual broadband speeds they can receive. This voluntary code is a significant step in this direction.”

The new code of practice was welcomed by the Ofcom Consumer Panel, which watches and advises the regulator.

“Ofcom’s strict monitoring of the code will be key to ensuring its success across industry and improving the situation for consumers," said Anna Bradley, chair of the group.

"We are delighted to see that Ofcom will be carrying out mystery shopping exercises and we will be looking carefully at the results. If they show that ISPs are not in compliance, it will clearly be time to call for a mandatory Code of Practice.”

Ofcom's announcement was also supported by the UK's Internet Service Providers' Association (ISPA). The trade association said it would like the code to be extended to cover wireless broadband providers as well as fixed-line operators.

ISPA also recommended that consumers should not choose their internet deals on the basis of price or speed alone.

"Like anything, you get what you pay for," said Hendrie-Liaño, chair of ISPA Council. "Customers should consider the features and specifications of ISPs’ services and select the most appropriate provider and tariff for their needs.”