Humza Yousaf has accused Kate Forbes of handing the Tories "so much ammunition" with which to attack the SNP's record in government.
In another stormy leadership debate on live TV, the health secretary turned his fire on his Cabinet colleague after she had previously questioned his suitability to replace Nicola Sturgeon.
Forbes, the finance secretary, had set the contest to become the next First Minister alight earlier this week after she attacked Yousaf's record as a minister.
And the Highland MSP tonight claimed to be the leadership candidate Unionists feared the most - only for Yousaf to insist that Conservatives were "rooting" for her to win.
During lively exchanges, the health secretary said he was proud of the job Forbes had done in government as well as his own ministerial record.
Yousaf continued: 'We’re only going to win support for our cause if we work together as a team.
"But what unfortunately happened in the last TV debate, Kate, is that you essentially gave our opponents so much a so much ammunition to attack us with.
"Douglas Ross said today that your words would be in every single Conservative leaflet.
"What you've done is you've handed the Conservatives, and our opponents, material and ammunition to attack and trash our record.
"Now we'll be hearing it every single week. They don't fear you - they are rooting for you to win so your words are heard."
Forbes hit back: “The future first minister is going to have to deal with a lot worse than we’ve been dealing with through this contest.
"They’re going to have to stand up to the UK Government, they’re going to have to stand up to the opposition – and they’re going to be accountable to the people of Scotland who want answers and they want to see competent delivery of results."
Yousaf, Forbes and fellow leadership contender Ash Regan were appearing on a Channel 4 News debate broadcast across the UK.
Speaking at the Engine Works events space in Maryhill, Forbes was asked if she wanted to apologise for trashing Yousaf's record.
She said: "We’re electing here, a future First Minister, who will have to deal with some very weighty matters,” she said.
"The SNP hasn’t had an election contest for 20 years, and I think we need the time and the space for robust, frank exchanges.
"I’m proud of the track record of our SNP government, I’m proud of the exceptional leaders we have, I’m proud of the team members that we have around the cabinet table.
"But in an election contest, people don’t want to hear that we’re just going to do what we’ve always done.
"If we just do what we’ve always done, then we’ll get the same outcomes, and all of us here are agreed on the need for reform."
Regan said it was "perfectly legitimate" to point out "strategic mistakes that we have made as a party".
"However, I don't think attacking people personally is appropriate."
She added: "I think this is the time for a brave heart, and not faint hearts."
Yousaf and Forbes also clashed over abortion buffer zones as a Bill is set to be introduced at Holyrood that would prevent protesters standing directly outside clinics.
Forbes has repeatedly said she would support the principle of the legislation but she refused to say if she felt abortion was morally wrong during the Channel 4 debate.
Yousaf suggested Forbes had been equivocal on the issue.
"When Kate was asked this question (about her support for buffer zones) the other day at a hustings, you said ‘with balance’,” he said.
"What I didn’t understand is what you mean by that balance?”
He added: “I think it’s right to ask what do you mean by that balance, would you allow, for example, prayer vigils?”
Forbes hit back: “This is an example where we see another candidate trying to poke holes and trying to erode the honest and solemn commitments I have made.
"It boils down to a question of honesty – does Humza accept my word when I say that I will uphold those legal protections and support buffer zones or not?”
Yousaf said the question had in fact been asked by abortion rights group Back Off Scotland - who wrote to all candidates calling for them to support the legislation.
Immediately following the debate, the group said on Twitter Forbes had "lied" during the debate in claiming she had replied - only to posting again minutes later to say a member of Forbes’ campaign staff had responded.
According to her campaign manager Michelle Thomson, the response was signed off two days ago but due to her error was not sent until Thursday evening.
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