Australian Competition and Consumer Commission (ACCC) has filed a new legal challenge demanding a ‘further judicial review’ of the A$11bn merger between Tabcorp and Tatts.

Having been approved on 20 June by the Australian Competition Tribunal (ACT), the merger between Tabcorp and Tatts was opposed at the time by the ACCC with claims that the deal would impact market competition unfairly as well as consumer pricing.

Now, the ACCC has filed a federal court order to review the ACT’s decision to approve the merger.

“The ACCC is alleging the tribunal made three reviewable errors,” ACCC Chairman Rod Sims said. “It is therefore seeking clarification of these three points of law, which are central to the tribunal’s assessment of Tabcorp’s proposed acquisition of Tatts.”

The new legal challenge risks dashing Tabcorp’s hopes of completing the merger deal in the coming weeks.

In its claim, the ACCC alleges the tribunal was wrong to think it had to be satisfied there would be a “substantial” lessening of competition before it could determine the merger would be detrimental.

Simms added that this was inconsistent with previous tribunal decisions, which had taken into account the detriment caused by “any” lessening of competition.

The application also says the tribunal failed to compare the likely future state of competition with and without the merger - a test the ACCC claims is "fundamental" in weighing the potential detriment the merger could cause.

The third allegation is that the tribunal placed too much emphasis on benefits such as cost savings, which would be favourable for Tabcorp but not necessarily for punters.

"We believe we had no option but to seek a review of these three, what we say, are reviewable errors, particularly because they set such important precedents for the decisions we have to make into the future," Mr Sims concluded.