Andrea Leadsom has suggested that having children gives her an advantage over Theresa May in the race to Downing Street, as the Home Secretary urged her rival to sign a pledge committing to a clean campaign.
The energy minister told The Times that being a mother "means you have a very real stake in the future of our country" but insisted she was not trying to make it an issue in the Tory leadership election.
Mrs Leadsom, who has two sons and a daughter, said being a member of a "huge family" was an important part of who she was.
However she later said that the reporting of her comments was "beneath contempt" and that she expected the newspaper to retract the article and its headline.
The comments in The Times come just days after the Home Secretary spoke about how her and husband Philip were affected by being unable to have children.
The energy minister said: "I am sure Theresa will be really sad she doesn't have children so I don't want this to be 'Andrea has children, Theresa hasn't', because I think that would be really horrible."
But she spoke of the extra perspective she had from being a mother: "It means you don't want a downturn but, never mind, 10 years hence it will all be fine. My children will be starting their lives in that next 10 years so I have a real stake in the next year, the next two."
In a highly personal interview with the newspaper, Mrs Leadsom said: "Genuinely I feel that being a mum means you have a very real stake in the future of our country, a tangible stake."
Asked to contrast herself with Mrs May, she said: "I see myself as one, an optimist, and two, a member of a huge family and that's important to me. My kids are a huge part of my life."
Mrs May told the Daily Telegraph she likes to keep her "personal life personal" but says that she and her husband "dealt with" the fact they couldn't have children and "moved on".
"I hope nobody would think that mattered," she said. "I can still empathise, understand people and care about fairness and opportunity."
Mrs Leadsom's comments came as the Home Secretary urged her to sign up to an agreement to campaign within "acceptable" boundaries and not to work with other parties after the energy minister attracted the support of prominent Ukip figures.
The energy minister, who backed a vote to leave the European Union, has received the endorsement of both Nigel Farage and Brexit campaign Leave.EU, which is led by Ukip donor Arron Banks.
Mrs Leadsom told The Times: "I'm no Ukip sympathiser, they don't advise me, I don't know them, I've never even met Arron Banks.
"My big hope in this campaign is that when we leave the EU that Ukip will be a thing of the past. Hate crimes? It's absolutely appalling. I reject the premise that it's to do with the campaign."
Mrs May's "clean campaign pledge" commits the two candidates to:
:: Stick to the spending limits set by the Conservative headquarters
:: Not co-operate "in any way" with other political parties, their donors, members or active supporters
:: Do "everything in our power" to ensure that supporters' campaigning on social media is "in good taste"
:: Ensure the campaign stays within "the acceptable limits of political debate"
:: Do "what is right for our party and the country as a whole"
Mrs May used the interview with the Daily Telegraph to try to reassure Brexit-backing Tories that she was committed to leaving the EU, despite backing a Remain vote.
She said: "If I am prime minister we will come out of the European Union and part of that will be control of free movement.
"But alongside that it's important to show how we can come through what will be I think some difficult times with a better, brighter future.
"It is very important that people see there is at bright future and we can re-engage that entrepreneurial spirit of the trading nation for which the UK has always been known - that dynamic, creative spirit."
She added: "I am very clear that Brexit means Brexit. But I don't think we should see people as Brexiteers and Remainers now.
"We have a job to do in making the best deal we can in coming out of the EU and I am very clear that I will deliver Brexit."
In a reference to former cabinet colleague Ken Clarke's unguarded description of her, Mrs May said: "Politics can do with some bloody difficult women."
Supporters of Mrs May lined up to attack Mrs Leadsom over her Times interview, but the energy minister accused the newspaper of "gutter journalism" and "despicable and hateful reporting" and demanded a transcript.
In a later statement Mrs Leadsom said: "I am beyond anger and disgust. The reporting of what I said is beneath contempt.
"In front of The Times correspondent and photographer, I made clear repeatedly that nothing I said should be used in any way to suggest that Theresa May not having children had any bearing whatever on the leadership election.
"I expect The Times to retract the article and the accompanying headline."
Scottish Conservative leader Ruth Davidson highlighted the lines that Mrs May's supporters had been given to say about Mrs Leadsom - "Andrea is clearly a talented politician and she has a bright future" but "doesn't have the experience the country needs" - and contrasted them with the energy minister's comments.
Ms Davidson tweeted: "In seven years, I've never once disclosed an internal briefing, but here's the TM campaign's brief on AL. Gulf in class."
She seized upon Mrs Leadsom's comment that Mrs May "possibly has nieces, nephews, lots of people. But I have children who are going to have children who will directly be a part of what happens next".
Ms Davidson said: "I am childless. I have nieces and nephews. I believe I - like everybody else - have a very real stake in our country."
Tory MP Sir Alan Duncan said: "I'm gay and in a civil partnership. No children, but 10 nieces and nephews. Do I not have a stake in the future of the country? Vile."