Vocus has asked the Australian Competition and Consumer Commission (ACCC) to investigate TPG's decision to increase its equity in Amcom with the intention of blocking the sale of Amcom to Vocus.
On Thursday morning, TPG announced that it would increase its stake in Amcom to 18.6 percent, citing the Vocus merger announcement from December as its reason for increasing its investment.
"TPG is a long-standing shareholder of Amcom, and advises the market that it intends to vote its shares against the announced scheme arrangement under which Vocus proposes to acquire all of the outstanding shares it does not own in Amcom," the company told the Australian Securities Exchange (ASX).
"TPG supports the continued operation of Amcom as a stand-alone business under the stewardship of the current board of directors and management team."
TPG said it has no intention of making a counterproposal.
In response, Vocus said on Thursday that it remains committed to the proposal, and that the Amcom board continues to recommend that shareholders vote in favour of the merger in the absence of a superior proposal.
"Given this background and the overwhelming positive responses to the proposed combination received to date, Vocus will continue to pursue a successful conclusion to the merger with Amcom, and will update shareholders as appropriate," Vocus told the ASX.
"Separately, Vocus intends to refer the recent developments involving TPG to the ACCC."
Some have speculated that TPG may employ the same tactic to attempt to block a potential merger between M2 and iiNet, should it decide not to beat M2's estimated AU$1.6 billion offer, which the iiNet board judged to be superior on Thursday.