The independence of a review of Western Australia's environmental watchdog has been questioned, after it was revealed the agency will help hand-pick who will undertake it.

Environment Minister Albert Jacob ordered the external review of the Environmental Protection Authority (EPA) in December in the wake of a Supreme Court decision declaring its approval of the Government's controversial Roe 8 highway extension project invalid.

Mr Jacob's office has confirmed the EPA will advise him on who should do the review, and the report will go to the agency first, before it provides a final report to him by the end of March.

WA Greens MP Lynn MacLaren said that process lacked transparency and would not restore public confidence in the watchdog, in the wake of two separate Supreme Court rulings in just over two years overturning EPA approvals of controversial Government projects.

"The EPA decides who does the review, it's an internal review within the EPA," Mrs Maclaren said.

"There's no scrutiny, no transparency into the public domain and no opportunity for the public to give submissions.

"It's appropriate to have a retired judge, for example, or someone of high reputation in the judiciary to look at this ... that would give us a little more faith that the review will be thorough."

The Roe 8 extension is the first stage of a planned $1.6 billion heavy haulage highway dubbed the Perth Freight Link, which the Government wants to build to connect Perth's eastern industrial suburbs to the Fremantle Port.

It involves extending Roe Highway to Stock Road, but Premier Colin Barnett has already shelved the second stage of the project extending into Fremantle and the port itself.

Mr Jacob wrote to the new EPA chairman Tom Hatton in late December to set the broad terms of reference for the EPA legal and governance review.

He has requested the review consider matters including the clarity, content and consistency of the EPA's policies and guidelines and the processes to ensure they are given due consideration during assessment and in the EPA's reporting.

It will also look at the EPA's practices for development and application of policies and guidelines.

Public submissions not appropriate, Government says

Mr Jacob is on leave, but in a statement Acting Environment Minister Helen Morton said she was confident the process outlined by Mr Jacob would ensure and independent and thorough review.

She said the people selected to do the review would be independent of the EPA and would not have any conflicts of interest.

She said because the EPA was an independent statutory authority, it was appropriate that report would first be provided to the agency and then to the minister.

"Given that this is a legal and governance review, there will be no public submissions," she said.

"However, the independent reviewers will determine the extent and form of consultation with stakeholders."

The Minister's office has also confirmed that the review will not consider any individual environmental assessments by the EPA, and all existing environmental approvals would remain valid unless determined otherwise by the courts.

Mrs MacLaren said that meant the Government had no intention of checking, in light of the Supreme Court's ruling on Roe 8, whether the EPA had made any other invalid approvals.

"That is such a disappointment," she said.

"The Government will leave it to community members to fundraise for expensive legal challenges if they have concerns that other decisions by the EPA have been made improperly."