Judge Ross Robson agreed to an application by Telstra, made last Friday, seeking an injunction to stop Optus using what Telstra claims are ads with false claims, the Australian Financial Review reported. The Victorian Supreme Court will decide the matter in a trial next week.
"I am satisfied that there is a serious question to be tried in relation to the allegations of misleading or deceptive conduct on the part of Optus," Justice Robson was quoted as saying.
"I am further satisfied that if I were to refuse the application, Telstra may suffer irreparable injury for which damages would not adequately compensate. Finally, I am satisfied that the balance-of-convenience test favours the granting of the injunctions sought by Telstra."
Telstra's claims are that Optus has used ads on billboards, street furniture and online to claim that it is the best mobile network in Australia.
Optus has challenged the use of the phrase "One world from Australia's best mobile network. Unlimited." which has been used on numerous Telstra billboard ads.
A Telstra spokesman was quoted as saying: "We are pleased the court has heard our case that the Optus network advertising is misleading and has put a stop to it pending a final hearing.
"Telstra's mobile network is the best in Australia, providing the greatest coverage and faster speeds in more places and we believe advertising that tries to suggest anything else is an attempt to mislead consumers."
An Optus spokesman said the company had come out on top in P3's 2017 survey, earning the title "Best in Test", and believed that this fact needed to be communicated to Australians.
"Unfortunately, our competitor is clearly unhappy about losing to Optus, and has no doubt lost its sense of humour in the process," he said.
"Optus believes Australians should know Optus has an alternative, award-winning premium mobile network that delivers great value for customers.
"Optus will continue to invest and compete for customers across cities, in regions and rural locations with a premium quality network that continues to improve, expand and deliver customers great value and must-have sports and entertainment content."