Western Australia's Environmental Defender's Office is challenging state environmental approval of the Roe 8 highway extension, which will cut through the Beeliar wetlands.

The office filed an application with the Supreme Court of WA, asking it to set aside Environment Minister Albert Jacob’s July approval, which came after the WA Environmental Protection Authority recommended he grant it.

The application was filed on behalf of the Save Beeliar Wetlands group, which has opposed the project since the state government first announced its commitment to build it during the 2008 state election, and on behalf of Carole de Barre, whose property adjoins the proposed extension.

Separately, the Greens say the Aboriginal heritage approval for the project should be deemed invalid.

It is a registered site under the Aboriginal Heritage Act for its ethnographic significance, but there has instead been a focus on its archaeological significance, Greens MP Lynne MacLaren said.

She said the site meant a lot to Nyoongar people as the birthplace of the Waugyl, a dreamtime serpent-like creature that was responsible for the creation of major waterways.

“Under the act, the presence or absence of archaeological evidence makes no difference to the protected status of a ethnographic site,” Ms MacLaren said.

“You could send 200 archaeologists to the site and they still would not find a Waugyl.”