Matt Hancock has hit out at Jeremy Hunt's "negative" leadership campaign.
The health secretary said the Conservative leadership hopeful had made a "mistake" by accusing his rival Boris Johnson of being a "coward" over facing public scrutiny.
Speaking to talkRADIO's Julia Hartley-Brewer, Mr Hancock said: "I think it is a mistake to have such negative campaigning.
"I think that Boris Johnson, like Jeremy Hunt, has been subject to huge amounts of scrutiny in this campaign."
Over the weekend, Mr Johnson's private life was thrust into the media spotlight after a row with his partner led to police being called to his home.
He has so far refused to answer questions about the incident, despite increasing pressure to do so.
But Mr Hancock said there was plenty of time for Mr Johnson to set out his plans for Brexit and beyond, and face scrutiny over those issues.
"They had a TV debate last week and there's another TV debate to come," Mr Hancock added.
"There is a dozen more of these hustings around the country. That's all for the good."
He continued: "Boris will be able to get over his optimistic positive agenda of delivering Brexit and then getting on to uniting the country, making sure people get more pay."