UK broadband providers have been instructed to include the cost of line rental in all internet package advertisements.
The Advertising Standards Authority (ASA) has given service providers three months to change the way they advertise their broadband deals.
From October 4th 2012, all broadband adverts must make it expressly clear how much it will cost to take out a package with broadband, related communication and entertainment services, and line rental.
The ASA issued the ruling after 18 complaints were received over a Virgin Media advert, which failed to incorporate line rental into the headline price.
"We understood that some consumers purchased line rental as a separate standalone service, for receiving incoming calls only, and therefore considered that line rental had a value associated with it in its own right, for which some consumers would generally expect to pay," the ASA stated.
"On that basis, we considered that line rental was a non-optional, conditional service, as opposed to a charge with no intrinsic value which formed an inherent and inseparable part of the advertised bundled products, and did not need to be included in the overall price."
However, the ASA said that because line rental had some of the characteristics of a charge, it was "particularly important" for the cost to be stated "sufficiently prominently".
The line rental cost was not presented clearly alongside the most prominently stated bundle prices in the Virgin Media adverts, the regulator said.
"In light of that, we considered that the ads did not make sufficiently clear the extent of the commitment consumers must make to obtain the advertised bundles and were therefore misleading," it added.
The ASA said it had issued a three-month grace period to the broadband industry, mindful of the impact the latest ruling will have on the way internet packages are advertised.