Image caption The BT advert was an instalment in the "Adam and Jane" campaign

An advert for telecommunications firm BT has been banned for misleading customers over broadband speeds.

In a TV advert, a voice-over said BT is "rolling out up to 20 meg speeds" to give "consistently faster broadband".

The Advertising Standards Authority, which received 17 complaints, said it had not seen sufficient evidence to support the claim and concluded that the advert was likely to mislead.

BT said it was disappointed by the ASA's adjudication.

After the complaints were made, BT told the ASA that the sequence shown in the advert had not been intended to be an actual comparison.

The advert - an instalment in an ongoing campaign about "Adam and Jane" - showed Adam being shown around a property by an estate agent as he talked to his partner, Jane, on his mobile.

She was seen viewing the house online from her home computer, loading a website faster than the estate agent at peak time, before a voiceover said: "BT is rolling out up to 20 meg speeds to give you a consistently faster broadband throughout the day even at peak times."

A similar message was carried in radio and press adverts.

There were 17 complaints from the public and competitors Sky, TalkTalk and Virgin.

Some felt the 20Mb (megabits per second) claim was misleading and could not be substantiated.

Others believed surfing a typical website would not be any faster with a 20Mb service than it would with BT's original 8Mb service.

And three people said the speed at which the "Jane" character navigated various web pages was faster than anyone could achieve at any connection speed.

Until the ASA comes up with its conclusions the way a "fast" internet connection is sold to consumers will remain a mess. Rory Cellan-Jones, BBC technology correspondent Read Rory's thoughts in full

In reaching its decision, the ASA said: "Because we had not seen sufficient evidence to support the claim that BT's new broadband service was consistently faster than its existing 8Mb service even at peak times, we concluded that the ad was likely to mislead."

The advertising watchdog said viewers could expect the internet speed demonstrated by "Jane" to be available to them, adding that this was not the case.

It concluded: "We noted BT's new service was available to fewer than half of all households and the roll-out, increasing that figure to 75%, was anticipated to take around two years.

"We noted that a significant proportion of the population could not get the service at the time the ad appeared and therefore considered the ad should have made that clear. Because it did not, we concluded that it was likely to mislead."

Highlighting 'higher speeds'

The watchdog ruled that the adverts must not appear again in their current form.

In a statement, BT said: "We are disappointed by the ASA's adjudication.

"At the time the ads appeared, BT had just started rolling out a new up-to-20Mb broadband service across the country and we wanted to highlight the higher speeds available in newly enabled exchange areas offering customers consistently faster web browsing in comparison to BT's up-to-8Mb service.

"There was certainly no intention to mislead."

It said the claims made in the advertising included independent data from broadband monitoring firm Epitiro and a statistician.