Internet service providers will have to be careful about advertising headline speeds for broadband connections after an advert by Bulldog Communications was criticised by the advertising watchdog on Wednesday.

The Advertising Standards Authority (ASA) said Bulldog's television ad, which contained the phrase up to 8 meg broadband for only 15.50 pounds per month, had breached its code.

The watchdog said the ad should be withdrawn because not all customers were able to benefit from the advertised 8 meg speed.

The ASA said the words up to were not an adequate qualifier in ads for higher speed services, given the impact that signal attenuation could have on speeds and performance.

It told Bulldog to amend the ads and in future to indicate prominently that top speeds vary significantly, affected as they are by signal attenuation, which is caused by distance from the exchange.

While people living near an exchange might expect 8 megabits per second (Mbps), those living further out could have to accept slower speeds.