Farrer MP David Farley said on Sunday One Nation's migration policy would include an extra 100,000 people annually, on top of the 130,000 it had already committed to.
The overall number would be about 5000 migrants more than the estimated 225,000 people under Labor's federal budget forecast.
Pauline Hanson corrected the comments on social media, stating her party's policy remained to reduce net overseas migration to 130,000 people.
Mr Joyce said Mr Farley had made an error in his comments on migration numbers.
"Show me a political career where people haven't made a mistake, and I'll show you a person who's not told the truth," Mr Joyce told Seven's Sunrise program on Monday.
"I'm not going to throw anybody under a bus. When people are new in parliament, they can sometimes get things incorrect, and that's what happens.Â
"God knows, I've done it enough."
Mr Joyce said One Nation's policy remained at 130,000 people annually for net overseas migration.
The latest Demos poll, published by Capital Brief on Monday, shows One Nation's primary vote falling to 24 per cent, with the coalition on 25 per cent, and Labor on 26 per cent.
It marks a slight turnaround in polling, after previous highs put One Nation rivalling support for Labor.
Prime Minister Anthony Albanese said Mr Farley's comments demonstrated that he agreed with Labor's migration policy.
"What it really has shown over the last couple of days is that One Nation, if there's one policy they've spoken about over the 30 years that Pauline Hanson has been active in politics, it's migration," he told reporters in Western Australia.
"They can't even get a policy on that."
Toowoomba-based coalition MP Garth Hamilton, who faces a One Nation challenge, said the opposition's migration plan was resonating with the electorate.
"There's plenty of work ahead of us, but Australians want us to get rid of Labor," he told AAP.
"This is just one poll but it shows Australians know that being angry isn't enough - you've got to have a plan and a disciplined team to deliver it."
Immigration Minister Tony Burke was set to make a speech at the National Press Club earlier in August and unveil a change to Australia's migration numbers.
However, the address was cancelled at the 11th hour because cabinet had not signed off on the policy amid internal disagreement.
The rise of One Nation in opinion polls has spurred a re-think on migration by Labor and the coalition.
Current migration numbers sit at about 301,000.
Opposition frontbencher Andrew Bragg raised eyebrows within the coalition - and earned a rebuke from party leadership - when he suggested capping overseas migration at 180,000 during an address to the National Press Club.
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