The campaigns were eye-catching, but what they did not freely disclose were links to a more powerful moneyed lobby, the Liberal Party and even the Prime Minister himself.

TV and online ads – including on Fairfax websites – compared the legalisation of same-sex marriage to an iceberg and said the change potentially carried negative consequences for children and human rights.

The campaign was paid for by a group incorporated a month before the ads hit airwaves: Marriage Alliance, which also commissioned polling reportedly showing same-sex marriage was a low priority for voters ahead of Tuesday's government party-room vote.

Behind this self-described collection of "individuals, businesses and community organisations" are volunteers with Liberal Party connections.

Marriage Alliance's directors include former federal Liberal president Ashley Goldsworthy, a 79-year-old who won an OBE for work as a computer scientist before building a high-flying career in real estate and higher education.

Like Mr Goldsworthy, fellow director James Dominguez​ is a knight of the Catholic Order of Malta. The former investment banker and coal executive has been a patron of the sometimes controversial World Congress of Families conference.

The Marriage Alliance's public face also has Liberal links.

PR firm Hugo Halliday, founded by the Liberal mayor of Ryde, Bill Pickering, is handling the group's media relations. (Nathaniel Smith, son of former NSW Liberal attorney-general Greg Smith, is managing the account.)

The group's spokeswoman is barrister and academic Sophie York, a former Liberal candidate for Brendan Nelson's seat of Bradfield, whose 2005 book Angels of Aceh was launched by Tony Abbott, whom Mrs York has known for nearly 20 years, according to statements she gave to other media.

Another group of "concerned people and organisations" took out a full-page newspaper advertisement this week

on the allegedly deleterious impact of being raised by same-sex parents.

The Australian Marriage Forum, founded in 2011, said the ad – at a cost understood to be in the order of $25,000 – was paid for by a direct-mail campaign to members.

But the group does not appear to have disclosed fully its affiliation to the Australian Christian Lobby.

The Marriage Forum notes the ACL is one of its many supporters, but records show its website is registered in the name of the Australian Christian Lobby president, Lyle Shelton.

"We felt there was a need for another voice in the debate," Mr Shelton said, while adding the links between the organisations are disclosed in registration documents lodged with the Queensland government.

The ACL – which the current Prime Minister and his Labor predecessor and Opposition Leader Bill Shorten have addressed – spent about $100,000 on campaigns and polling last financial year. It received $150,000 in donations. The ACL proposed in May a national plebiscite on same-sex marriage, an option the government will now consider instead of a free vote in Parliament, which it voted against on Tuesday night.

It is not known how the Marriage Alliance funded its campaign. A 30-second prime-time TV spot costs up to $35,000.

Mrs York could not be reached for interview and there was no response by deadline to a message sent to Mr Goldsworthy.

A crowd-funding campaign for the Marriage Alliance last week achieved about half of its $20,000 target.

But a spokesman for the group denied that the organisation was linked to another Catholic group that opposes same-sex marriage in more strident terms: Defending Natural Marriage.

"There is no direct link [between the two]," the spokesman said. "Marriage Alliance believes the rights of children are being subjugated by arguments about equality between gay and heterosexual adults."

Defending Natural Marriage, which posted photos from the Marriage Alliance's launch on its Facebook page, and to whose website the Alliance links, warns of an "agenda being pushed on society by homosexual activists".