Peter Dutton says the Liberal Party will remain "true to our values" under his leadership, with policies aimed at "forgotten Australians".
He made the comments in Canberra after being elected unopposed as the party's new leader, with Sussan Ley to serve as deputy.
"We'll propose strong policy ... our policies will be squarely aimed at the forgotten Australians in the suburbs across Australia," he said.
"Under my leadership, the Liberal Party will be true to our values, that have seen us win successive elections over the course of the last quarter of a century.
"Make no mistake, and Australians understand this, the next three years under Labor is going to be tough for the Australian people. Already they're breaking promises and foreshadowing policy shifts. They weren't ready to govern."
When asked whether he would support , Mr Dutton acknowledged he "made a mistake" when he walked out of former prime minister Kevin Rudd's apology to the Stolen Generations in 2008.
He indicated he would be willing to speak to the Albanese government about the Voice to Parliament for Aboriginal and Torres Strait Islander Peoples.
"I made a mistake in relation to the apology and largely that was because of my own background and experience," he said.
"I worked in Townsville, I remember going to many domestic violence instances, particularly involving Indigenous communities, and for me at the time I believed that the apology should be given when the problems were resolved and the problems are not resolved."
"I think we have all been on a unity ticket to do as much as we can to improve the condition in local communities, the advancement of Aboriginal people in our country, education, health outcomes, closing the gap, all the rest of it, but we have all failed, and so, yes, I understand the symbolism and I made that mistake."
Deputy leader Sussan Ley also vowed to advocate for rural and regional Australia, and said she would be a "strong voice" for women.
"We know that we didn't receive the support of all women at the last election, and my message to the women of Australia is we hear you," she said.
"We're listening. We're talking. And we are determined to earn back your trust and your faith."
Former prime minister Scott Morrison - who stepped down as leader of the party following the Coalition's federal election loss - congratulated Mr Dutton and Ms Ley.
"They are incredibly experienced, well versed, are deeply committed Australians to both the Liberal cause and because of the nation and I think they'll do an outstanding job," Mr Morrison said.
"I look forward to giving them all of my full support."
David Littleproud named leader of Nationals
Member for Maranoa David Littleproud has been elected leader of the Nationals, defeating former leader Barnaby Joyce and Victorian MP Darren Chester in a party room vote.
NSW senator Perin Davey has been named deputy leader.
Mr Littleproud described it as the "proudest day of his professional life".
"I believe passionately in the National Party because we are all there is about regional and rural Australia. We are the conscience of rural and regional Australia right here in this parliament," he said.
"This is the proudest day of my professional life, to lead a party that, over the last 40 years ... has guided me, guided me to who I am and what I am."
"The National Party today starts its journey towards 2025, with a vibrant team, ready to articulate the policies that are important to regional and rural Australia."
Mr Littleproud said he would draw on the experience of former deputy prime ministers Barnaby Joyce and Michael McCormack to "build a bridge of unity and purpose" and "make sure that regional and rural Australia isn't forgotten".
Barnaby Joyce 'not really' sad following defeat
Following the party room vote, Mr Joyce released a statement congratulating his successor.
"I suppose you think I am sad. Not really," he said.
"I gave every ounce of my energy to make sure that I looked after the people of regional Australia, the people in the small family businesses, the people in the weatherboard and iron, the people on the farms, making sure that we drove the investments to make their standard of living ahead."
"I want to congratulate David, Perin and Bridget. They have a mighty task ahead of them and I will give them all the support I can."
'We must be doing something right': Barnaby Joyce
Earlier, Barnaby Joyce made his case on the Seven Network ahead of the party room meeting, saying the junior coalition party must be doing something right given it retained all its seats at the federal election.
"We won every seat we had before the election, we had three retiring members and still won the seats (and) we were in striking distance of one of the two seats we will be able to take in the next election," he said.
"The Liberals lost 19 seats."
"In the last two elections, that I've been the leader, we've only picked up seats. We must be doing something right but the job is not over."
Leader of the Nationals Barnaby Joyce speaks to the media during a press conference at Parliament House in Canberra. Source: AAP / LUKAS COCH/AAPIMAGE
More women in senior positions
Queensland Liberal MP Stuart Robert said earlier that former defence minister Peter Dutton and former environment minister Sussan Ley's run for the parliamentary positions would not be contested.
"Peter Dutton ... and Sussan Ley will be sworn in by the party room uncontested," he told the Nine Network on Monday.
"(I'm) super happy about the party room and the leadership team we're bringing in."
Mr Robert also said he expected there would be more women on the Liberal front bench, following a reshuffle after former ministers lost their seats in the 21 May election.
"We've got so many talented women in our ranks and you'd expect that talent to be recognised and rewarded," he told Sky News.
"So absolutely, I'd expect far more women just because of the calibre of the women in the Liberal and National parties."
The party room will also discuss some of the lessons to be learned from the Coalition's federal election defeat.
"The party room is the opportunity for everyone to get together, to have a conversation, to share how things have gone, not just to elect their leadership team," Mr Robert said.
"I'm one of the few MPs who was actually here in 2007 (when the coalition also lost), so the time to provide some guidance on what it means in opposition and how we hold the government to account, that will come later."
Mr Dutton will become the first Queenslander to lead the Liberal Party.
The Dickson MP has been touted as Scott Morrison's likely replacement since the coalition lost government.
Mr Dutton, a former police officer, spruiked his credentials for the job of opposition leader following his nomination.
"In a prime minister you need someone who won't buckle in hard times and will stand up for our country and I have proven that in the portfolios I've had," he wrote on Facebook.
"My work ethic is second to none and I have the skill and experience having served five leaders and have learnt from each."
Mr Dutton has pledged to take the party back to its core values and represent the aspirational "forgotten people" of Australia.
"We aren't the Moderate Party. We aren't the Conservative Party. We are Liberals," the post said.
