Prime Minister Malcolm Turnbull has warned drownings at sea could resume if Labor wins the election.
He also stepped in to defend his immigration minister, insisting Peter Dutton's remark that many refugees are illiterate was a "statement of fact".
"Our opponents in the Labor Party and the Greens who promote more open borders cannot evade the awful consequences of the last time they tried this experiment," Mr Turnbull writes in Fairfax newspapers on Friday.
Mr Turnbull said he begged former prime minister Kevin Rudd to maintain Howard government border protection policies when he was opposition leader.
Instead, he wrote, 1200 people drowned at sea.
"Kevin Rudd's party did not have a commitment to strong borders any more than Bill Shorten's party does today.
"There is nothing generous about policies that lead families to drown at sea."
Opposition immigration spokesman Richard Marles has meanwhile given an "absolute guarantee" Labor won't soften its border protection policies after the election, insisting the party had learned "the hard way".
"There is absolutely no way we are about to shift from it, not in this election and not in government," he told News Corp.
"You can't go through the experience we did, in government, and seeing 1200 people perish on our border and not be utterly seared by that experience."
He said despite several Labor candidates and MPs publicly criticising Labor's policy on offshore processing of asylum seekers, the policy reached at the party's national conference last year was not negotiable.
"Since that decision has been made there is not a single, senior figure within the Labor Party who has done anything other than completely back that position in."
