Greens MP Lynn MacLaren has introduced a private members bill in the Western Australian Parliament to allow same sex marriages.

It comes on the same day the High Court overturned the ACT's same sex marriage laws, meaning the unions of 27 couples who wed last weekend are now invalid.

Ms MacLaren described the High Court's decision as disheartening.

"I know that campaigners around Australia will be poring over the judgement and the ACT Attorney General said today that they too will be looking at that judgement and how they can move forward," she said.

"It's important that people don't lose heart. We are going to reform marriage in Australia and whether it's at a federal level or at a state level, we'll continue to do that.

"Today I introduced a same sex marriage bill for Western Australia and it's different because it sets up a new system of marriage, alongside other marriages, and it's distinctly different from the ACT bill and I'm hoping that it will pass through the parliament.

"It doesn't seek to do what the ACT bill sought, it just deals with our state laws... so I can't see it affecting the federal Marriage Act."

In introducing the bill, Ms MacLaren told Parliament the legislation has been designed to comply with Commonwealth laws.

"Similar bills have been introduced in Victoria, and South Australia, and New South Wales and Tasmania, this Bill is a different bill, I have learned from those experiences and the Same Sex Marriage Bill before you has been amended according to what we've learned from those other experiences," she said.

"Where the Australian Parliament has faltered, we can succeed."

Ms MacLaren says research now shows most Australians now support same sex marriage and it is time politicians recognised this.

"I want the government to take it on and recognise that it's an important thing that should be considered and progressed in Western Australia," she said.

"All of Australia has been attempting this, it's a change that time has come, and I think it's something that Western Australia can do in a leadership role for the rest of Australia to say that same sex marriages can be implemented and it's not going to undermine society or scare anybody, it's just going to be a way for people who love each other to be fully accepted in society."

Federal campaign continues

Meanwhile, WA Labor MP Stephen Dawson hopes campaigners continue to pressure the Federal Government to legalise same sex marriage.

Dennis Liddelow and Stephen Dawson during their marriage outside Parliament House in Canberra on Saturday. ( AAP: Alan Porritt )

Mr Dawson married his partner Dennis Liddelow in the ACT over the weekend.

He says despite their marriage now being annulled, they will continue to fight.

"Nobody can take away from us the ceremony we went through on the weekend," he said.

"Nobody can take away those positive images of those Australians who got married on the weekend.

"Our marriage is annulled so we start over again from scratch, and both Dennis and I and the other couples will continue to campaign.

"The pressure is now on Tony Abbott and the Federal Parliament.

"Over 60 per cent of Australians support marriage equality for same sex couples so the ball is in his court."