Gay rights advocates in Australia argued in the country’s highest court on Tuesday to prevent the government from surveying the public on whether gay marriage should be legalised, AP reported

The petitioners want Parliament to decide on the subject without consulting the public and are arguing in the court that the government does not have the constitutional power to start a postal survey next week.

Opinion polls show most Australians want same-sex marriage legalised, but many of its advocates question how representative of Australian attitudes the postal survey would be.

A seven-judge bench will hear two similar cases over Tuesday and Wednesday in Melbourne. They could rule on the validity of the survey as early as Wednesday and prevent ballots being posted to voters from September 12.

One of the cases was brought to court by independent lawmaker Andrew Wilkie and gay rights campaigners Felicity Marlowe and Shelley Argent. The second case was filed by Janet Rice, a senator in the minor Greens Party who is married to a transgender partner, and the Australian Marriage Equality lobby group.

Despite the legal cloud hanging over the postal survey, acrimonious campaigns on both sides of the argument are gathering pace.

The survey and objections

The survey is the second choice of Prime Minister Malcolm Turnbull’s conservative government, after the Senate refused to approve funds for a rare, compulsory vote known as a plebiscite.

If a majority who take part in the survey wants marriage equality, Parliament will be allowed to decide on the matter by December. But a few lawmakers have said their votes in Parliament would not be swayed by public opinion, raising questions about why the public is being surveyed at all.

Turnbull and Opposition leader Bill Shorten support gay marriage. But the prime minister’s predecessor and intra-party rival Tony Abbott is a vocal opponent.

Many yes-vote supporters argue marriage equality is, as the United States Supreme Court found, a human right that should not be subjected to an opinion poll.