Liz Truss launched a blistering attack on Nicola Sturgeon - branding her an "attention seeker" and saying the best way of dealing with her is to "ignore her".
The Foreign Secretary made the undiplomatic remarks at a hustings event in Exeter, where she and Rishi Sunak were grilled by Tory party members.
Meanwhile Mr Sunak was once again accused of disloyalty to Boris Johnson - which he denied, but added: "The government was on the wrong side of a very serious ethical problem."
Asked about the Scottish First Minister's call for a second referendum on Scottish independence, Ms Truss said: "I think the best thing to do with Nicola Sturgeon is ignore her. She is an attention seeker. That is what she is."
In a varied series of questions from party members - who will decide the next PM despite accounting for just 0.3% of the population - the Foreign Secretary was also pressed on her views on bloodsports, and whether she would push for hunting to be allowed again.
Ms Truss told of her “strong support” for bloodsports - but appeared to rule out scrapping the fox hunting ban.
The Mirror told last month how in 2017 she spoke of wanting to axe the ban, which was introduced by Labour in 2005.
Asked by a Conservative activist if she would make time as PM to repeal the law, she signalled she would not open the “Pandora’s Box” of fox hunting.
She told activists: “I’m an MP in Norfolk which is a fantastic place for country sports.
“We have a very strong shooting industry - I’m very, very supportive of country sports.”
But she told the Tory member who wanted the hunting ban abolished: “While I share your love of rural pastimes and I am a strong supporter of all the fantastic conservation work the shooting industry does, I think I have to be very careful about opening that box.”
Meanwhile Mr Sunak said that if he wasn't a politician his dream job would be running Southampton Football Club, and when asked about his most embarrassing moment he said: "I struggled to pay for petrol in a car that wasn't mine."
The former Chancellor was famously pictured filling a car on a Sainsbury's forecourt in a backfired publicity shot.
He was asked how he would support mental health services by a man who said his 16-year-old daughter was told she faced a two year wait for vital support.
"For a child that's appalling," the audience member said. "We were in the fortunate position that we could go private... since then we've been unable to get any support for her or her family."
"There's more we can do" admitted Mr Sunak - saying that he wants to provide more mental health provision in education settings and protecting young people online.
Mr Sunak was challenged by a woman who works in social care for the elderly, who told him: "It needs to be fixed sir."
He conceded that services need to be improved, and said workers need to feel "valued and fulfilled".
Elsewhere Ms Truss said she would never again sanction a lockdown, claiming she was not involved in formulating key Covid measures.
Activists applauded as she claimed she would tackle illegal immigration, raise defence spending to 3% of GDP by 2030 and signalled she would stop solar panels being placed on farmland.
The bandwagon-leaping Cabinet Minister also vowed to “channel the spirit of the Lionesses” who “fought bravely against the odds” following their 2-1 extra time victory over Germany in the Euro 2022 women’s football final.
Bookies believe Ms Truss has a 91% chance of beating Mr Sunak to No10.
The former Chancellor also won claps when he echoed Ms Truss’ solar panel pledge and supporters cheered as he lashed out at his rival’s tax cut plans - despite his own promises to slash income tax.
Warning inflation was the biggest economic problem gripping the UK, he said: “I’m not going to do things that risk making the problem far worse and last for longer - especially if that means borrowing tens of billions of pounds in unfunded promises which we just add on the country’s credit card and then ask our children and grandchildren to pick up the tab.”
Basking in the glory of England's dramatic Euro 2022 win, the Tory leadership favourite said: "I will channel the spirit of the Lionesses who fought bravely against the odds and got things done and delivered a massive victory."
Her campaign was given a massive boost with the endorsement of trade minister Penny Mordaunt, who at points last month was the favourite to reach No 10.
Ms Mordaunt told the audience: "I could have remained undeclared, I could be off sipping piña coladas, but I'm not. I'm here with you because this is too important and I'm not going to leave that to chance."
She said of Ms Truss: "She knows what she believes, in her resolve to stand up against tyranny and for freedom, what's what our country stands for. With her we can win."
Ms Truss said securing Nazanin Zaghari-Ratcliffe's freedom was among her biggest achievements, stating: "That was one of the best moments of my life. That's why I'm in politics, to make a difference."
Mr Sunak, despite spending more than two years as Boris Johnson's chancellor, earlier insisted he is "definitely the change candidate" rather than offering continuity.
He said: "You say I was in Boris Johnson's government, remember, Liz is, I think, the longest-serving Cabinet minister in the Cabinet at the moment and she was in the Cabinet before I was even an MP, so it's hard to say I'm the one that's been around a long time."
The weeks since Boris Johnson's resignation has been characterised by blue-on-blue infighting as huge splits emerge within the Tory party.
Earlier today Ms Truss said she was running a "positive" campaign after Nadine Dorries - one of her most high-profile supporters - shared a doctored image of Mr Sunak sticking a knife into the former PM's back.
It sparked a huge outcry among Conservative MPs, who pointed out that it is less than a year since colleague Sir David Amess was murdered.
The Foreign Secretary said she had been "very clear" with her team about the type of campaign she wanted to run.
Culture Secretary Ms Dorries, a high-profile supporter of Ms Truss, shared a doctored image on Twitter that portrayed Mr Johnson as Julius Caesar with Mr Sunak as one of the assassins.
A string of Conservative MPs - mostly supporters of Mr Sunak - quickly condemned Ms Dorries and branded the attacks on the former chancellor as "dangerous" in the wake of the murder of Sir David Amess.
Asked about Ms Dorries' actions, Ms Truss said: "I've taken Twitter off my phone for the duration of this campaign.
"I've been very clear with all of my team, I'm running a positive campaign. This is about growing the economy, it's about unleashing the potential right across the UK."
Work and Pensions Secretary Therese Coffey, Ms Truss' campaign manager, told Times Radio it was Ms Dorries' personal choice to post the message.
Ms Coffey said: "Well, I wouldn't have done it. The Liz for Leader campaign certainly didn't do it. Nadine chose to do it. I've made her aware that many colleagues were upset by it.
"It's for Nadine to decide how she runs her social media. But all I say is that I'm really here to focus on Liz rather than other news."
She added: "I'm not going to go into individual conversations, but she recognised that other people would have been upset by some of this, but she's very keen to make the case herself."
The former chancellor was asked about accusations he is a "backstabber" on the BBC Radio 4 Today programme, but said he would not comment specifically on "what others are choosing to say".
He added: "I will tackle the broader claim that they (the accusations) relate to, because I do think there is a risk that people are looking at the last few months of the Government with slightly rose-tinted glasses about what it was really like.
"Because it wasn't working as it should, and crucially the Government found itself on the wrong side of a very serious ethical issue, and, for me, also going down the wrong economic path, and that's why in the end more than 60 MPs at the last count, I think, resigned from the Government, of which I, after a lot of deliberation and months of standing by the PM, was one of them."
