The merger of Australian betting firms Tabcorp Holdings and Tatts Group could be on hold after the country’s competition watchdog filed to block the union.

On Monday, the Australian Competition and Consumer Commission (ACCC) announced it had applied to the Federal Court for a judicial review of last month’s decision by the Australian Competition Tribunal (ACT) to grant approval of Tabcorp’s multi-billion dollar acquisition of rival Tatts.

The ACCC had previously expressed reservations regarding the merger of Australia’s two betting and lottery giants, based on the watchdog’s belief that the union would significantly lessen competition in certain gambling sectors. The ACCC singled out racing broadcasting rights and the ability of Tabcorp-Tatts’ rivals to pursue regional wagering licenses as particular areas of concern.

Sensing that the regulatory winds weren’t at their back, Tabcorp-Tatts chose to withdraw their ACCC application and apply instead to the court-run ACT. The ACT gave its thumbs-up based on its view that the union offered consumers more potential benefits than harms.