Andrea Leadsom has said she "deeply regrets" smoking cannabis at university.
The Conservative leadership contender said she was "not proud" of taking the drug, and advocated for "strict laws" around drug-taking.
"I tried cannabis at university and I deeply regret it," she told talkRADIO's Julia Hartley-Brewer.
"Since then, as an adult, I have discovered the very real impact that cannabis taking can have on your mental health in particular, and particularly since cannabis is now very often so much stronger than it was when I was 19, 20."
She continued: "It is a really important issue that young people need to be aware of, that it can seriously damage your mental health."
News of Ms Leadsom's experience with drugs emerged over the weekend, following fellow leadership contender Michael Gove admitting he had used cocaine in the past.
However, she maintained that medicinal cannabis should be accessible to those in need.
"There is another side to cannabis which is medicinal cannabis. I do think it's important that we enable people to access it for relief of symptoms when it's under strict medical supervision."
On the issue of Brexit, Ms Leadsom said the UK should leave the EU on October 31, "no ifs, no buts".
"We have to accept that we're leaving at the end of October," she said. "It is a hard red line. We have to accept that the Withdrawal Agreement Bill is dead."
Currently, Ladbrokes place odds of 8/1 on Ms Leadsom becoming the next Conservative Party leader.
But she said she was confident that she had the backing of the eight MPs necessary to continue in the contest, and was "very much looking forward" to it.
"I'm backing myself. I believe I've got a very workable three-step plan for a managed exit from the EU," she added.
"To have a credible negotiation you always have to be prepared to walk away."