The announcement follows a ruling of “unacceptable circumstances” by the Takeovers Panel last week against Alinta’s 10.25% purchase of APT’s stock. About a fortnight ago, Alinta paid $56.5 million to acquire an initial 4% stake.

At the time, Alinta said it would appeal the panel’s decision, which effectively stops it acquiring any more of APT’s units without making a full takeover bid.

APT is seeking a court order, which will run in parallel with the panel’s proceedings that requires the divestment of all the newly purchased units.

“APT has been concerned that Alinta is seeking to obtain control of APT without giving all APT unitholders the chance to participate and receive a premium if control of APT passes,” APT said in a statement to the Australian Stock Exchange.

“By seeking to move to a position where it owns 40-50% of the units in APT, Alinta appears to have moved to block any competition from other bidders for APT and thereby limited the price that it would have to pay for control of APT.”

If the planned merger between Alinta and Australian Gas Light goes ahead, Alinta will inherit AGL’s 30% stake in APT. However, the Australian Competition and Consumer Commission (ACCC) requires it to divest that holding within a year of the merger’s approval by shareholders.