Malcolm Turnbull prepared to take a drug test in defence of proposed welfare drug checks

Malcolm Turnbull once famously admitted he had smoked pot, and now the prime minister says he would be prepared to take a drug test.

Mr Turnbull is defending the government's planned trial of drug tests for 5000 Newstart and Youth Allowance recipients.

Anyone who tests positive will have their welfare quarantined, while those who fail more than once will be referred to medical professionals for assessment and treatment.

Asked during a Huffington Post Facebook Live interview on Thursday whether he would be happy to undergo a test himself, Mr Turnbull said he would.

"I would be happy to undergo a drug test at any time," he said.

The measure is designed to help welfare recipients who have a drug addiction and get them back into work.

Earlier, Finance Minister Mathias Cormann said he too would be happy to undergo a test.

"Yes, happy, no worries, any day," he told reporters.