The Takeovers Panel has ordered the sale of Alinta's 10.25 per cent stake in the Australian Pipeline Trust (APT).

The panel has ordered that the units in APT which Alinta acquired under the acquisitions be vested in ASIC (Australian Securities and Investment Commission) for sale by a stockbroker or investment bank selected by ASIC and that the net proceeds be returned to Alinta, the panel said.

The panel said Alinta and The Australian Gas Light Company (AGL) would be prohibited from acquiring the APT units under a bookbuild but could acquire them under takeover offers for all of the units in APT.

The panel prohibited Alinta from acquiring or disposing of units in APT until schemes of arrangement to merge Alinta and AGL are implemented or the merger agreement between Alinta and AGL lapses.

The panel's final orders relate to Alinta's acquisition of 10.25 per cent of APT units in the period August 16-22 and follow the panel's recent decision to declare unacceptable circumstances over the share grab.

Alinta, which operates over 20,000km of gas pipes and 12,000km of electricity lines in Western Australia and Victoria, made a lightning raid on APT's units last month.

The move confused market-watchers at the time, because when Alinta's planned merger with AGL is complete, it will inherit a 30 per cent APT stake, but the Australian Competition and Consumer Commission (ACCC) requires it to divest that holding.

However, the strategy became clearer when a few days after the Takeovers Panel's initial declaration, Alinta presented the ACCC with a new proposal for a possible takeover that would see it sell APT's interests in the Moomba to Sydney Pipeline, Parmelia Pipeline and GasNet Australia Group.

APT is in the process of taking over GasNet, which last week reiterated its recommendation for the $452 million offer, while the trust waived the bid's conditions in an attempt to expedite the deal.

Alinta said on Sunday that it would take legal action in the Federal Court seeking a review of the panel's ruling of unacceptable circumstances in relation to the 10.25 per cent stake in APT.

It is hard to fathom how the Takeovers Panel have arrived at this ruling, Alinta chief executive Bob Browning said.

Alinta firmly believes it has broken no law by acquiring this stake, nor done anything unacceptable.

We consider that the panel have erred in their ruling and their orders have failed a fundamental logic test.