From Monday, 80 cannabis cafés, or coffee shops in 10 Dutch local authority areas will only sell marijuana from licenced growers, as the main part of a lengthy experiment with regulating production kicks off.

Arnhem, Almere, Breda, Groningen, Heerlen, Maastricht, Nijmegen, Tilburg, Voorne aan Zee and Zaanstad are taking part in the experiment, which is set to run until 2029.

The aim of the experiment, first mooted in 2018, is to assess if licencing marijuana production has an impact on organised crime and user health. However, the outlets will not yet have legal hashish on the menu because uncertainties about the supply, justice minister David van Weel told MPs last week.

Government inspectors will monitor the cafés from Monday to ensure they sell only official cannabis, with hashish set to follow on 10 June if possible. Since last year, the shops have been selling both legal and illegal marijuana products.

Tilburg coffee shop owner Willem Vugs told broadcaster NOS last week that the licensed growers had initially focused on producing legal weed and that hashish is more complicated. He welcomed the delay, saying: “I am pleased growers are getting more time to produce the right quality and variety.”

The experiment aims to phase out the Dutch policy of gedogen, or turning a blind eye, a strategy that has decriminalised the possession of small amounts of cannabis and licensed sales outlets, but still prohibits bulk production and sales.

This “front door, back door” system was introduced in the 1970s to draw a distinction between so-called “soft” and “hard” drugs, at a time when Amsterdam was gaining a global reputation as a haven for drug users.

Policymakers now want to close that back door.

Breda mayor Paul Delpa, one of the main campaigners for a regulated system, told Dutch News last year the experiment is fundamentally about safety.

“The Dutch policy for weed is quite devious. People can buy it legally in coffee shops, but the production of the weed and the buying part (the back door) of the shop owners is illegal. That means there’s a big criminal world that thrives on producing the weed and selling it to the shops. That needs to change.”