A day after state and federal Liberal MPs pulled out of the World Congress of Families in the face of a political backlash, US campaigner Larry Jacobs added to the controversy surrounding the event by claiming poverty could be reduced if only children were raised in traditional families.

"We have to find the truth, and the truth says that statistically there is no better place for a child to be," said Mr Jacobs, the congress' managing director, and an ardent supporter of Russia's anti-gay laws. "Ninety per cent of poverty can be solved simply through the affirmation of marriage."

Mr Jacobs' address kicked off what was always going to be a divisive forum, with organisers forced to change venues four times in recent weeks in the face of planned protests against the extreme views of many of its speakers.

On Friday, federal Families Minister Kevin Andrews and state Attorney-General Robert Clark - who were scheduled to give opening addresses at the conference - pulled out after learning it would be hosted at a new venue run by Catch The Fire Ministries, an ultra-conservative Christian group whose outspoken leader Daniel Nalliah once blamed the Black Saturday bushfires on Victoria's abortion laws.

But despite the late withdrawals, dozens of protesters gathered at the entrance of the venue on Saturday, heckling guests as they entered. One protester managed to sneak in as a registered guest, storming the stage and pouring fake blood over herself in front of NSW MP, the Reverend Fred Nile and his wife.

"We don't want your backyard abortions," she yelled, before being marched out.

Guests at the event were visibly rattled by the breach and turned to prayer as the woman was ushered outside. But despite ongoing protests at the gate throughout the day, the rest of the conference was incident free.

Controversial American breast cancer doctor Angela Lafranchi was one of the headline acts, pushing research suggesting a link between abortion and breast cancer. Reverend Nile, leader of the NSW Christian Democrats, called for more Christians to get involved in politics. And Paul Hanrahan, the executive director of Family Life International Australia, used his speech to suggest abortion was worse than terrorism in Syria.

"Many people lately have been upset at the terrible atrocities being committed in the name of religion in Iraq and Syria and other places. Terrorists and terrorists' kids holding severed heads is certainly gruesome. Answer me this: how is it worse?" he asked.

The decision by Mr Andrews and Mr Clark to pull out of the conference comes only three months before the Victorian election. On Friday, state Liberal MPs Bernie Finn and Jan Kronberg also withdrew, averting ongoing concerns from moderates within the Liberal Party and claims from Labor of "right-wing extremism".

However, speakers at the conference hit out at the decision, with Mr Nalliah calling it "gutless" and Dr David van Gend from the Australian Marriage Forum saying it sent a bad message to the protesters who had sought to disrupt the event.

"By not coming to this conference our MP friends have encouraged this feral mob to do it again," he said.

Outside, protesters gathered throughout the day, some heckling attendees or calling them bigots as they tried to enter. A group of demonstrators called the Block Party Against Hate entertained the crowd in more peaceful fashion, with a burlesque show and a "rainbow" ice bucket challenge targeting Prime Minister Tony Abbott.

US cosmologist Lawrence Krauss came along to the protests in Hallam, saying that as a scientist he was happy to fight the people whose religious beliefs are so strong that they "invent ridiculous information".

One protester, Sam Castro from the Whistleblowers, Activists and Citizens Alliance said she was hit in the back of the head by one of the World Congress of Families attendees on their way in Saturday morning.

With Tessa van der Riet