Pauline Hanson on Monday brought forward the motion, which also declared “anti-white” racism was on the rise in Australia.
The phrases have been used by far-right groups to stoke racial division.
Prime Minister Scott Morrison says the government’s support was “regrettable” and Porter says it was his office’s fault.
“An early email advising an approach on the motion went out from my office on this matter without my knowledge,” Porter said in a statement on today.
“This one was not escalated to me because it was interpreted in my office as a motion opposing racism.
“The associations of the language were not picked up. Had it been raised directly with me those issues would have been identified.”
Indigenous Affairs Minister Nigel Scullion and his cabinet colleagues Michaelia Cash, Simon Birmingham, Mitch Fifield, Matt Canavan and Bridget McKenzie all voted in favour.
The motion was defeated 31-28 despite support from the government.
But they will get a chance to change their position officially when the vote is recommitted today.
“As leader of our team in the Senate, I take responsibility for that and apologise to the Senate,” Government Senate leader Mathias Cormann told parliament.
He accepted a challenge by Labor’s Senate leader Penny Wong to recommit the vote.
Porter said he was reviewing the processes in his office, which had put government senators in a difficult position because their advice was to vote for the motion.
In the Senate, I opposed it as racist bigotry and said it could have been written on toilet paper. Govt senators were jeered in the chamber as they sat down to vote with Hanson. The Cormann-Porter excuse can’t fly.
— Derryn Hinch (@HumanHeadline) October 15, 2018
Cormann said when the One Nation motion first came up in September the government decided to oppose it and instead make a statement saying they deplored racism of any kind.
But during the Senate debate, Liberal senator Anne Ruston made a one-line statement about deploring racism – before the Coalition senators present voted for the motion, instead of against.
Opponents say the motion was plucked straight out of the playbook of far-right activists.
“This is a phrase used by white supremacists,” Wong told reporters.
Hanson took advantage of the government vote to make media appearances and promote video of the debate.
“Looks like Scott Morrison is suffering from a bad case of it’s okay to be white guilt,” she tweeted on Tuesday.
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