The Federal Government has decided to appeal against the release of sensitive documents relating to the Perth Freight Link project, with retired Labor MP Alannah MacTiernan lashing out at the move.

The Administrative Appeals Tribunal recently ordered the federal Department of Infrastructure and Regional Development (DIRD) to hand over the documents to Ms MacTiernan, deeming them to be in the public interest.

Ms MacTiernan said the DIRD had advised her of its plan to appeal against the decision in the Federal Court, dragging out the already two-year battle over the release of the documents under freedom of information (FOI) laws.

"Extraordinary, I mean it really is," she said.

"To go to this end to protect a series of documents that are aimed at showing the way in which this project was planned tells us that there is some deep embarrassment about the way this project was devised."

The 75 documents in dispute relate to early planning and could shed light on the Federal Government's decision to commit $1 billion towards the project.

Ms MacTiernan accused her political opponents of deliberately dragging out the matter until after contracts are signed for the Roe 8 extension, the first stage of the project.

Earlier this week, Premier Colin Barnett said he expected the contracts to be signed within months and for work to begin before the March 11 state election.

"I suspect they're hoping to bide time until the contracts have been signed," Ms MacTiernan said.

"We will go into the court and seek to get some expedition of a hearing so that this matter can be brought to a head in a time frame that gives us, the public, the taxpayers some time to make some judgements before the contracts are signed.

"I still care very deeply about getting a good outcome for the people of this state."