Bill Shorten has headed off a revolt within Labor over his decision to support asylum seeker boat turnbacks.

Left faction delegates made a impassioned plea to the 397-member national conference in Melbourne on Saturday to rule out turnbacks, as they imperil asylum seekers and breach Australia’s international obligations to refugees.

However, the vote was lost on a show of hands.

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A second Left motion, which was also defeated, called for the closure of offshore detention facilities if they don’t meet “humane and safe conditions”.

Victorian Labor MP Andrew Giles, who moved the resolution against turnbacks, was interrupted by angry protesters who unfurled a banner on stage reading “No refugee towbacks”.

Mr Giles registers his vote. Photo: AAP

Their appearance was met with loud applause by some but the protesters were swiftly thrown out by security staff.

Mr Giles said he was unconvinced by the effectiveness of turnbacks.

“I regard them as inherently unsafe and they are quite clearly contrary to our international obligations,” he said.

“I see them as an impediment to developing the safe legal pathways we are all committed to.”

Mr Shorten, who spoke last in the debate, said the issue was not only about safety at sea, but “the Australia we want to see in the mirror”.

“I would not be the leader I seek to be of this nation if I ignored my own personal belief and conviction on this matter,” the Labor leader said.

“In all conscience, if we know that people are getting on boats and we know that some of them sink and people drown … I cannot take to the Australian people at the next election, a policy which I believe may contribute to that outcome because of our decisions. I cannot do that.”

Labor immigration spokesman Richard Marles passionately told the conference his party would bring to the asylum seeker issue its values of fairness, generosity and compassion, but needed the full suite of measures to stop deaths at sea and end people smuggling.

Speaking at the opening of the second day of the conference, Mr Shorten revealed that shadow cabinet had approved a new asylum seeker policy including turnbacks, $450 million for United Nations refugee efforts, a doubling of the humanitarian intake and new oversight of detention centres.

“We must never allow people smugglers to take advantage of a perceived weakness and so a Labor government must have the option of turning back boats, provided it is safe to do so,” he said.

Protesters have their banner removed by security. Photo: AAP

Frontbencher Tony Burke, Labor’s last immigration minister before leaving office in 2013, gave an emotional speech in support of boat turnbacks, reflecting on the 33 people who died on his watch.

“I want us to help more people than we’ve ever helped before but I want everyone to get here safely,” he said.

“I have no doubt whatsoever if we give hope to the trade we will end up helping fewer people… and hundreds will start the journey but never complete it.”

Burke also spoke emotionally of one of the 33 who died – a 10-year-old child. He said he found out the child’s name and stuck it to his desk with a Post-It note as a reminder.

A Labor government from day one would seamlessly continue the coalition’s policy of turning back boats coming from Java to Christmas Island.

Asylum seekers coming on boats from source countries such as Sri Lanka and Vietnam would be assessed either at sea or on land, depending on operational circumstances, with the oversight of the UN High Commission for Refugees.

The use of lifeboats could also continue.

Immigration Minister Peter Dutton said Labor’s support of turning back boats was “a deal not a policy”.

“Labor will weaken our borders again and blow a massive hole in the budget,” he said.

– with ABC