Attorney General Jim McGinty says new prostitution laws should be in place by Christmas.

The Attorney General, Jim McGinty, is confident new prostitution laws will be in place by Christmas, despite the Liberal Party's plan to fight the legislation.

Under the legislation, brothels would be able to operate legally for the first time and it would be up to local councils to approve them.

The Liberals yesterday decided to oppose the Bill over concerns it will lead to a proliferation of brothels in the suburbs.

Mr McGinty says the legislation has the support of police and councils and he is positive it will be approved by Parliament.

"I'm confident there is a majority in both houses of Parliament to be able to pass this legislation," he said.

"This is legislation we have to have to be able to put the health of sex workers and their clients on a proper basis and be able to regulate local government planning considerations and most importantly be able to put police beyond corruption.

"This is about making a tough decision but a necessary one. A police Royal Commission said we should legalise brothels to avoid corruption. This has been something on the agenda for government's of both political complexions for quite some time now. It takes a strong government to be able to deliver these changes."

Greens MLC Giz Watson says the Liberals' concerns are unfounded.

"That's just a bit of political stirring and fearmongering about this issue," she said.