Broadband provider Virgin Media has been ordered to pull an advertisement following complaints from rival firms BT and Sky.
The Advertising Standards Authority (ASA) told Virgin Media that is 'Stop the broadband con' campaign violated UK marketing rules.
Through its online adverts, the broadband provider accused other firms of failing to keep their download speed promises.
Virgin Media said the ads were designed to highlight "widespread dissatisfaction" among consumers about how broadband deals – and particularly speeds - are advertised.
However, the ASA ruled that the firm has gone beyond highlighting the disparity it believes exists across the industry between advertised broadband speeds and those delivered.
"[The advert] implied that other broadband providers dealt with consumers dishonestly in relation to broadband speeds," the authority stated.
John Petter, Managing Director at BT Retail, told the BBC that he welcomed the ASA judgement.
He argued that Virgin Media's campaign for the industry to use 'average' rather than 'up to' speeds relied on "misleading broadband users to make its point".