Michael Gove showed "rank hypocrisy" by using cocaine as a young journalist, according to a spokesman from the Transform Drug Policy Foundation.
Danny Kushlick said it was "hypocrisy at the highest level" for the politician to have used the class A drug around the same time he wrote an article slamming "middle-class professionals" who took drugs.
"There is rank hypocrisy at the highest level to have penned an article around the time when he was using, and knew other people were using in his flat," Mr Kushlick told talkRADIO's Julia Hartley-Brewer.
"The rank hypocrisy is vast, but if we stopped politicians standing for Parliament or leadership for rank hypocrisy, there wouldn't be very many left."
Mr Gove's cocaine use is the latest in a string of drug confessions from Conservative leadership contenders.
Rory Stewart admitted to smoking opium whilst in Iran and Jeremy Hunt said he had a cannabis lassi whilst holidaying in India.
Andrea Leadsom confessed to smoking cannabis at university, and Boris Johnson hinted that he had taken "icing sugar" which he thought was cocaine at the age of 19.
Dominic Raab has also admitted to using cannabis as a student.
"What we have is a situation where significant numbers of politicians have used illegal drugs, but still support the drug war," Mr Kushlick continued.
"The drug war is negatively impacting on the lives of millions of people all over the world, causing mayhem, gifting £350 billion trade to organised crime, causing violence, messing up Mexico and Afghanistan and numerous countries in Africa, and poor deprived marginalised communities in the UK."
The solution, Mr Kushlick believes, is to stop the criminalisation of drugs.
"When we criminalise, all we do is increase the harm. We kill people," he said.
"Repeated governments have said drugs are illegal because they are dangerous. The drugs that are most dangerous, the ones that kill people most, the ones that cause the most violence are alcohol and nicotine.
"This isn't about being pro-drug or anti-drug, this is about having a successful government policy that delivers for the needs of the most marginalised and disadvantaged."