Two Plusnet adverts selling business broadband have been ruled "misleading" by the UK Advertising Standards Agency.
The ads, which were seen on Facebook in March, had headlines claiming unlimited business broadband from £4.50 a month. But the small print said an extra £10.50 a month would be required in line rental.
Plusnet defended the ad, claiming that because the adverts were aimed at business users, who they described as having a "higher level of competence and knowledge than a typical consumer", the exclusion of line rental from the headline price was acceptable.
Domestic broadband prices in advertising have to include all costs, according to an ASA ruling last year. This rule did not apply to business adverts, to which Plusnet also referred when responding to the complaint.
Following the ruling, all companies who advertise their business broadband in this fashion will have until May 15 to change the ads to include all costs.
Plusnet changed its ads after the investigation began, making the price of line rental more obvious before the ASA made its ruling.
During its investigation, the ASA also questioned why the delivery fee for a new router was not included in the advertised price. Plusnet said it did not have to since a router was not a compulsory purchase.
However, the ASA said the price of line rental and router delivery were not clear enough, therefore making the ads misleading.
It said it considered the average user to be "reasonably well-informed, observant and circumspect", and that Plusnet's assertion that business customers would not be misled was false.
It also ruled that the router delivery fee should be included in the adverts as it concluded that most users would take the new router when signing up.
Plusnet was told that upfront and overall monthly costs must be clear in its future adverts for all potential customers, and that the offending adverts must not be used again in their current form. ®