The war on drugs has been "nothing short of a disaster" and it is time to study other options, including decriminalising possession of drugs and legally regulating their production and supply, Mr Ainsworth said.
Referring to the legalisation of alcohol in the United States after 13 years of prohibition, he said: "After 50 years of global drug prohibition it is time for governments throughout the world to repeat this shift with currently illegal drugs."
The Labour backbencher, who was previously a Home Office drugs Minister, went on: "Politicians and the media need to engage in a genuine and grown up debate about alternatives to prohibition, so that we can build a consensus based on delivering the best outcomes for our children and communities.
"Prohibition has failed to protect us. Leaving the drugs market in the hands of criminals causes huge and unnecessary harms to individuals, communities and entire countries, with the poor the hardest hit.
"We spend billions of pounds without preventing the wide availability of drugs.
"It is time to replace our failed war on drugs with a strict system of legal regulation, to make the world a safer, healthier place.
"We must take the trade away from organised criminals and hand it to the control of doctors and pharmacists."