Pyne slams 'red herring' marriage claims

Christopher Pyne hit out at campaigners who say the survey is about freedom of speech and religion.

A senior Liberal has warned opponents of gay marriage to stop making red herring arguments against change as enrolments for the postal vote closed.

Enrolments closed at midnight on Thursday with both sides of the debate from politicians to celebrities making a last ditch plea for people to get involved.

Survey papers are expected to start hitting mailboxes in mid-September.

Cabinet minister Christopher Pyne hit out at "no" campaigners who claim the survey is about freedom of speech and freedom of religion.

He said the only question was whether two members of the same sex could marry and any questions about protections for religious freedom would be dealt with by legislation if a majority of Australians voted in support of marriage equality.

"It is a complete red herring," he told ABC TV.

"So, let's keep it simple and try to not muddy the waters, as some people do, which is quite frankly a campaigning tactic."

It followed warnings by the Melbourne Archbishop Denis Hart that future gay marriage laws could infringe rights of freedom of religion and conscience.

"It could result in restrictions on the right of ministers of religion and religious bodies and organisations having the freedom to teach, preach and speak about marriage between persons of the same sex being contrary to their religious or conscientious beliefs," he wrote in an open letter.

Archbishop Hart urged Catholics to vote against change "for the health and future" of society.

But he insisted the debate needed to be respectful, with both sides expressing their ideas with conviction instead of creating a campaign of hate.

Mr Pyne said any colleagues who insisted on opposing gay marriage in parliament despite a "yes" vote would have to explain themselves to their electorates.

"I certainly wouldn't be thumbing my nose at the will of the Australian people," he said.