The Australian Competition and Consumer Commission (ACCC) planned to call an expert witness to explain what could be achieved at 64 Kbps internet speeds in its case against ISP Optus' "supersonic" broadband plans.

The competition watchdog filed the suit in the Federal Court last week.

It contended that advertisements for Optus' upgraded HFC network, which boasted internet speeds were "supersonic", did not "sufficiently or clearly disclose" that users would be throttled to 64 Kbps once they exceeded an allocated data allowance.

The commission proposed in the Federal Court today "to put on a telecommunications expert who will say what 64 Kbps does, [including] what programs it can and can't be used to access".

"I expect it will be uncontroversial but as I only told our friends [at Optus] about it today, they may wish to put on an expert in response," the commission said.

The parties agreed to hearings for the case starting October 27, although Justice Nye Perram queried whether the dates were early enough given the commission's desire to fast-track proceedings.

The commission said that, although it contended "the advertisements were misleading and should be dealt with as quickly as possible", the late October dates represented a good balance of the parties' respective interests.

The hearings, expected to run over two non-consecutive days, would deal with all issues in the case except penalties, which the parties agreed to "be dealt with at a later date".

The commission was seeking injunctions, "civil penalties, corrective advertising and costs" from Optus and had sought to "fast-track" hearings in the Federal Court to resolve the matter quickly.

Optus said last week it was "distressed" by its status with the ACCC and had "never intended nor sought to intentionally mislead" customers via its advertisements.

It was "working with the ACCC" to resolve the latest complaints, it said.

The telco was also involved in a case with the ACCC over its unlimited broadband and phone bundles.