Conservative leadership contender Robert Jenrick has attacked his rival, Kemi Badenoch, accusing her of being "disrespectful" to Tory members by failing to set out policies.
The pair are in the final stretches of a campaign to replace Rishi Sunak, who led his party to an historic defeat at the general election in July.
Jenrick, who trailed Badenoch for support in the last voting round of MPs, has previously signed up to the yellow card penalty system introduced at the start of the contest and intended to stop "blue-on-blue" infighting.
He has put policy on immigration - and a commitment to leaving the European Court of Human Rights (ECHR) - at the heart of his campaign, whereas Badenoch has accused Jenrick of offering "easy answers" on the issue.
Conservative Party members are currently taking part in an online vote after the field was whittled down to two in a series of votes by MPs.
The vote ends on 31 October, with the victor to be announced two days later on 2 November.
Jenrick said Badenoch needed to set out her stance on “the big issues facing our country”, including whether the UK should remain a member of the ECHR.
He told BBC Radio 4's Westminster Hour: "I think it’s disrespectful to the members and the public to ask for their votes without saying where you stand on the big issues facing our country today.
"A plan today is what I offer. A promise of a plan at some point in the future is what my opponent offers, and I don’t think that’s the way to rebuild the public’s trust and confidence in us."
He insisted that all Conservatives who wanted to stand as a candidate at the next election would have to sign up to leaving the European Convention on Human Rights (ECHR) if he became their leader.
Badenoch has not ruled out leaving the ECHR, but has repeatedly said there needs to be a bigger plan and not just "a throwaway promise to win a leadership election."
Her pitch is that the party needs to return to "first principles" and be clear about what it stands for, rather than "throwing out numbers" and "easy answers" or setting out new policy promises or targets that may not be kept.
The duo have two more weeks to make their case to the Conservative members before Sunak's successor is announced.
The leadership contest has been running since July, when six candidates entered the race, overseen by 1922 committee chair Bob Blackman.
At the time, Blackman said he wold give a yellow card and a public dressing down to any candidate who attacked a rival during the campaign.
He said "constant backbiting and attacking colleagues" by Tory MPs during the last parliament was a key reason "why the party did so badly in the general election".