The Australian Competition Tribunal has approved the proposed A$11 billion merger between gaming rivals Tabcorp and Tatts Group.

The only condition imposed by the tribunal today is that Tabcorp must press on with the already agreed sale of its Queensland gaming machine monitoring business.

"The tribunal is satisfied in all the circumstances that the proposed merger would result, or would be likely to result, in such a benefit to the public that the acquisition should be allowed to occur," tribunal president Justice John Middleton said in a statement.

The ACT is set to make its formal determination on Thursday, but made its decision public after shares in both companies were placed in a trading halt.

Tabcorp in April agreed to offload its Odyssey gaming machine monitoring business to smooth the merger after the Australian Competition and Consumer Commission expressed concerns over competition in the sector.

The ACT today said public detriments identified by the ACCC were unlikely to arise or not of significance.

"The ACCC does not propose to comment until the reasons for decision are public, but notes that the net public benefit test the tribunal was required to apply is different to the substantial lessening of competition test the ACCC undertakes in its informal merger clearance process," the ACCC said in a statement.