Scott Morrison’s star recruit Warren Mundine has slammed Australia Day as “invasion day” and urged the government to change the date.

In an embarrassment for the Prime Minister, who has campaigned on Australia Day for weeks, Mr Mundine is an unabashed supporter of the move to change the date.

Just three years ago, Mr Mundine, a former ALP president who will join the Liberal Party on Wednesday, urged Australia to dump the January 26 celebration.

“I’ve always thought of Australia Day as Invasion Day. I think the date needs to be changed,” Mr Mundine said.

In 2017, Mr Mundine again argued for the change in an opinion piece in Sydney’s Daily Telegraph.

“The 26th of January is the wrong day to celebrate Australia Day,” he wrote.

“Australia Day should be celebrated on January 1. That’s the proper day to celebrate Australia’s independence, identity and nationhood because that’s the day Australia came into being and it’s a day everyone can unite behind.”

However, just weeks ago, after he started talks with Mr Morrison to consider a tilt at politics with the Liberals, Mr Mundine started to change his tune. While he still supports changing the date, he said the debate was harming the country.

“This all needs to stop,” he told Sydney radio 2GB.

“It irritates me that every time it comes up. Every year, you get the same old people coming out and arguing the same old cases, trying to divide the country when we should be actually trying to work together.”

Mr Morrison has repeatedly attacked Bill Shorten on the Australia Day issue, prompting the Opposition Leader to confirm the date would not change under a Labor government.

The Prime Minister confirmed early on Wednesday that Mr Mundine would run for the Liberals in the ultra-marginal seat of Gilmore. The party’s preselected candidate, Grant Schultz, was dumped on Tuesday at the instruction of Mr Morrison’s supporters to make way for the Aboriginal leader.

Dumped Gilmore candidate has quit Liberal Party and says his dead dad Alby would be “rolling in his grave” at ⁦@ScottMorrisonMP⁩ moves to parachute in ⁦@nyunggai⁩ https://t.co/MJR5oCrEij — 𝕤𝕒𝕞𝕒𝕟𝕥𝕙𝕒 𝕞𝕒𝕚𝕕𝕖𝕟 (@samanthamaiden) January 22, 2019

Mr Schultz has compared the decision to overturn his democratic preselection with the actions of Labor’s “faceless men”, and said he would run as an independent.

“They are not representing the people and that’s why I resigned,” Mr Schultz said.

The fight for the southern NSW seat could soon become three-way, with Deputy Prime Minister Michael McCormack confirming his party will also field a candidate.

“The Nationals are considering running a candidate in Gilmore,” he said.

Labor has seized on the Coalition in-fighting, rushing out a new attack ad arguing Mr Mundine lives “hours” away from his seat and supports nuclear power.

But the Prime Minister has defended his decision to parachute Mr Mundine into Gilmore.

“Warren has demonstrated his leadership ability over many decades, including the role he has played in reforming our welfare system, and has a deep understanding of what matters to Australian families and the pressures they face,” Mr Morrison said.

“He has strong values on the importance of family and working hard, on respecting each other, and has demonstrated a real ‘no excuses’ policy when it comes to getting things done.”

Mr Mundine has previously spoken of his deep regret over the breakdown of his second marriage.

“I never thought of myself as a bloke who was attractive to women but after I became president [of the ALP], it was like I became sexy to some people,” he said.

“If you look at pictures of me back then, I was 30 kilograms heavier, so I don’t really get it. But I was getting offers. And the ego got the better of me and I took one of those offers, and I got what I deserved, which was a divorce.”

His ex-wife later accused him of telling her she was ”too Aboriginal”, a claim Mr Mundine rejected as “bizarre”.

Sydney University academic Lynette Riley, who was married to Mr Mundine for 25 years and raised seven children with him, told The Sydney Morning Herald: ”He absolutely said it. It is seared into my brain. I was really shattered. I always thought of Warren as my soulmate.

”I think he has sold out his family and his culture. I think he gave up his good Aboriginal wife and kids so he could do that.”

Mr Mundine married his third wife, Elizabeth Henderson, in 2013. She is the daughter of Gerard and Anne Henderson, directors of the conservative Sydney Institute. He has described their marriage as “a new life”.