“Sexual radicals have launched a smear campaign to discredit the conference.”

The anti-gay marriage, pro-life group, World Congress of Families has issued an open letter to Australia just days before it is to hold a conference in Melbourne.

The letter on the WCF website has been written to respond to what it claims has been "unremitting and grossly misleading attacks" in the lead-up to Saturday's conference at St Cecilia's school hall.

"Sexual radicals have launched a smear campaign to discredit the Melbourne conference, which misrepresents the international pro-family movement and the positions of the World Congress of Families," it reads.

The letter has been signed by 80 prominent pro-life people including the former US presidential candidate and Arkansas Governor Mike Huckabee.

Several Australian politicians have been criticised for supporting the WCF's conference, including Senior Coalition Minister Eric Abetz who defended some of the groups more spurious claims, such as discredited links between abortion and breast cancer.

As reported by BuzzFeed in May, one of the main purposes of the regional conference will be the awarding of a special WCF honour for Australian Government Minister Kevin Andrews.

World Congress of Families

World Congress of Families / Via worldcongress.org

"The goal of sexual radicals is to deconstruct marriage... Like all social experiments that attempt to create a 'new man', these are doomed to failure," reads the letter published by Managing Director of the WCF, Larry Jacobs (front row, second from left).

The WCF regional conference is being organised by the Endeavour Forum, with the full rundown of the event available here.

The groups are also expected in Canberra on Wednesday for an anti-gay marriage summit dubbed 'National Marriage Day' held in Parliament House, as reported by BuzzFeed last week.