The Advertising Standards Authority (ASA) has warned BT about the information provided by its 'availability checker' feature.
A complaint was filed about the service - which allows people to find out what broadband services are available in their area - after it said download speeds of between 23 Mbps and 33 Mbps were available in a particular location.
The individual who made the complaint claimed this information was misleading and could not be substantiated as such a speed was not actually attainable in their area.
After investigation, the ASA upheld the grievance and has ordered BT to ensure the availability checker service provides more accurate information.
"Because the website included a download claim related to a specific address which was not available to that consumer, we concluded the ad was misleading," the authority stated.
This is not the first action taken against broadband providers by the ASA, as a number of companies have been forced to withdraw adverts that made misleading claims about their services.