Speaking to journalists at a leadership hustings event at Westminster, Mr Javid said his experience witnessing the impact of drugs on his community as a child made him “very hesitant” to consider the policy.
Drugs deaths in Scotland are at record levels in modern times, with 934 record in 1997 - double the UK average, and twice as many as 20 years ago.
Glasgow has seen an “unprecedented spike” in the numbers of deaths and overdoses, driven largely by the growth of street valium, and the Scottish Government has assembled a task force to respond to what it says is an “emergency”.
Asked whether he would reconsider his position as Prime Minister, Mr Javid referred to reports about past drug use by rival leadership candidates and said: “Call me the odd one out in this contest, but I didn’t take any drugs.
“And part of the reason was that I grew up on street in Bristol that was the centre of the local drugs trade.
“I think I would be very hesitant to look at anything that might increase drug usage. Anything I do would be designed to get people completely off drugs, because they are a cancer on our society.”