The advertising regulator will this week order broadband providers to give customers a more accurate picture of the internet speeds they can receive.
After an eight-month investigation, the Advertising Standards Authority (ASA) said it would allow broadband suppliers to advertise speed claims only if 10 per cent of customers could actually receive that level of service.
It called the move a "significant tightening" of its existing policy and said it had taken the steps to ensure adverts "do not mislead, including by the omission of important information". It is understood that the ASA could release its full conclusions as early as tomorrow after circulating the preliminary results of the consultation to the industry.
The findings follow criticism from the telecoms watchdog Ofcom about the difference between the speeds internet firms advertise and those they can actually provide. The Ofcom chief executive, Ed Richards, said earlier this year: "We would like to see clearer information provided to consumers which more accurately reflects the likely speeds they will actually receive."
The ASA first examined the issue of misleading speed claims in advertising last year, and launched an inquiry in January. Providers are understood to have unanimously agreed to the key 10 per cent provision. The ASA, however, has acknowledged this may not be enough and will demand that providers specify the speed range that between 20 per cent and 80 per cent of customers will receive.
The ASA's preliminary report, which has been seen by The Independent, said that in the advertising "the omission of important information may cause the average consumer to make a transactional decision he would not otherwise have taken".
One industry insider said the final conclusions were unlikely to be dramatically different from the preliminary report. The ASA would not confirm the exact date of publication, but had set a deadline of before the end of this month. A spokesman said an announcement would be made this week, although he did hint that there could be a delay.
Elsewhere in the report, the ASA will demand that the average speed must also be listed in the main part of the advert, not hidden away in the small print stating the terms and conditions. One provider has already criticised the "typical speed range" element, saying it was "confusing at best".
Ofcom has published several reports which showed the actual average broadband speeds companies offered against those advertised. In many cases there was a significant difference.
In its July publication, the telecoms watchdog revealed that while the average advertised speed in May was 15Mb, the actual average speed received by broadband users was only 6.8Mb. It showed that the average gap between the level advertised and achieved had widened since its previous report.
The ASA's recommendations apply only to broadband companies using copper wire, which covers 75 per cent of the existing network.