A group of ‘rainbow rebels’ within the Turnbull government has conceded that a ‘no’ vote will kill off hopes of same-sex marriage during this Parliament.

The High Court on Thursday paved the way for the government’s $122 million postal survey to go ahead, ruling against two separate challenges brought by same-sex marriage advocates.

Liberal MPs Trent Zimmerman and Tim Wilson, part of the group of MPs who suggested they might defy the PM and support a free vote, both said on Thursday that a ‘no’ result would end the issue until at least the next election.

The concession heightens the stakes for the postal survey as the Australian Bureau of Statistics prepares to begin mailing out ballot papers next week.

Hard yards on both sides

Both campaigns quickly claimed underdog status as soon as the decision was handed down.

“This is going to be a tough campaign but we are in it to win it,” Australian Marriage Equality co-chair Alex Greenwich said.

“But certainly the task ahead is daunting and clearly, having had this process imposed upon us in this circumstance, we are clearly the underdog.”

Australian Christian Lobby managing director Lyle Shelton, a prominent ‘no’ campaigner, said his side was facing a “David and Goliath battle”.

“We don’t have the resources that the other side do,” he said.

The Coalition for Marriage will focus on “the freedoms that will be effected, freedom of speech, freedom of religion and this issue of radical LBGTIQ sex-education”, which Mr Shelton claimed would be affected by same-sex marriage.

“That will be our message. It will be done in a respectful and courteous say at all times,” he said.

Hours before the court’s decision, the ‘Yes’ campaign also released a new television ad that features former Olympic swimmer and gay Australian Ian Thorpe.

Together, let's get it done.#VoteYes pic.twitter.com/6THxn7aOW9

— AU Marriage Equality (@AMEquality) September 7, 2017

During Question Time, Prime Minister Malcolm Turnbull welcomed the court’s decision, saying it would give Australians the chance to have their say.

While he said he would be voting ‘yes’, he again did not commit to campaigning on the issue.

Opposition Leader Bill Shorten said he and Labor would immediately intensify their campaign for a ‘yes’ vote.

“We want to say to people who are feeling disappointed, ‘Please turn your disappointment into determination. Determination to win’,” he said.

“I won’t be in the sidelines in this debate. Neither will the Labor Party and my colleagues.”

Labor has said it will campaign for a ‘yes’ vote. Photo: AAP

Asked by The New Daily what he would say to LBGTI Australians considering a boycott, Greens leader Richard Di Natale said: “I say, ‘Don’t do it.’ … Get involved, join the movement and if the Prime Minister wants to hear from people, make sure he hears from them loud and clear.”

Former prime minister Tony Abbott said it was a “pity” some same-sex marriage advocates wanted to “deny” the public their say.

“Nevertheless the High Court has spoken … I very much hope you’ll vote to protect the family,” Mr Abbott said in a video posted online.

The government also confirmed it would introduce legislation for advertising protections similar to those provided for in the electoral laws.

Labor and the Greens said they would support the legislation while stressing that the protections should be as strong as possible.

Earlier, Mr Turnbull rejected an offer from Mr Shorten to campaign together in support of a ‘yes’ vote.

“I’m interested in the assumption that the Leader of the Opposition makes that joining his signature to mine would actually increase the case for the ‘yes’ vote,” he said.

Asked by The New Daily if he would share a platform with other Coalition frontbenchers voting ‘yes’, Mr Shorten said: “We will all work with everyone.”

Ballot papers will now be mailed out from Tuesday with the result of the survey to be announced on November 15.