Bill de Blasio often boasts of being the mayor that stopped people getting arrested for low-level marijuana possession. Yet there were 17,880 arrests last year for personal marijuana consumption, nearly all of them for smoking in public rather than for having marijuana on their person. The number is considerably lower than under Michael Bloomberg, the previous mayor, but the racial disparity of those arrested is shocking: 86% of those arrested were people of colour. In Manhattan, the figures are even more stark: a New York Times investigation found black people were 15 times more likely to be arrested for possession than white people.

Those figures have pushed De Blasio to go further, instructing the NYPD to stop arresting people caught smoking in public, and to issue a summons instead.

De Blasio is not able to immediately change NYPD policy, but his statement is likely to influence a review of marijuana procedures currently taking place. It also comes just days after the Manhattan district attorney Cyrus Vance announced he would be ending prosecution in all marijuana possession and smoking cases after 1 August.

The move seems like another step towards New York legalising marijuana for recreational use. De Blasio is putting together a taskforce to prepare the city for outright legalisation, Governor Andrew Cuomo has set up his own “marijuana legalization taskforce” and Democratic senator Chuck Schumer has backed a bill for federal legalisation.

It comes during a year when many local and state-level lawmakers have been in conflict with the White House and federal drugs policy. While marijuana is legal for recreational use in states like California and Alaska, and decriminalised in a further 13, Attorney General Jeff Sessions has attempted to end a policy of federal non-interference in states with marijuana friendly laws – although he has found a lack of support in Congress.

Gubernatorial primary candidate Cynthia Nixon has said New York is still moving too slowly and made the racial disparity in marijuana arrests a central part of her campaign. She said: “For white people, the use of marijuana has effectively been legal, for a long time. Isn’t it time we legalize for everyone else?”