What is Sadiq Khan really up to with his call to decriminalise cannabis?

Calls for a shift in drug policy from the mayor of London, Sadiq Khan, will raise eyebrows in the highest echelons of the Starmer government.

The recommendations of the London Drugs Commission to decriminalise possession of “small quantities” of cannabis for personal use are nothing remarkable in themselves, being part of a tradition of debate in British drug policy about how to strike the balance between prohibition and legalisation.

However, the home secretary, Yvette Cooper, has already ruled out any change, claiming it would be politically incendiary for the current government to liberalise laws on cannabis and undermine its efforts to woo traditional Labour voters in the north of England and the Midlands.

How, then, should Khan’s intervention in such a controversial arena be judged if it is not an attempt to influence the current government’s thinking?

One interpretation is that Khan, like other mayors, is asserting his independence from the powerful elected representatives in the Labour Party. Indeed, as mayor of the capital, Khan has the largest individual mandate of any politician in Britain.

Although Keir Starmer’s ministers profess support for devolution in decentralising power across the UK, mayors pose acute problems for the prime minister and his government’s strategy. It has never been clear what approach Starmer should take if mayors advocate policies that undermine Labour’s agreed national position.

Khan had an explosive disagreement with the leadership before the last election because of his decision to expand the Ultra Low Emission Zone (Ulez), which antagonised voters in the outer boroughs. This position was believed to have cost Labour support in the 2023 Uxbridge by-election, in which the Conservatives unexpectedly triumphed. Labour in Westminster then rejected Khan’s proposal to impose rent controls on the capital.

Differences between national and London Labour are inevitable, not least because Khan has assembled a coalition of voters that leans towards the centre-left: he won again in 2023 by mobilising voters in the capital who in the past were tempted to support the Greens or the Liberal Democrats. Voicing support for a change in drug policy, alongside a liberal stance on migration and cultural diversity, appeals directly to the younger, professional, middle-class demographic that increasingly shapes London’s politics.

In contrast, Starmer’s team nationally have fought to win over the small-c conservative “red wall” by emphasising their commitment to tough immigration controls. In response to Starmer’s “island of strangers” speech, Khan said diplomatically: “Those aren’t words I would have used,” while underlining that migrants aren’t “spongers” or “skivers”. Meanwhile, the mayor of Greater Manchester, Andy Burnham, voiced support for a ceasefire between Hamas and Israel long before the national leadership adopted that position (as did Khan), and recently made clear his visceral opposition to benefit cuts.

Another explanation is that Khan is attempting to strengthen his power base, as thoughts turn to his future beyond the London mayoralty, having already served three consecutive terms. The UK Labour Party is London-dominated, and Khan has a strong position from which to advance his career, potentially by returning to parliament either as an MP or a member of the House of Lords.

From there, the door would be open for a return to the cabinet. As a former lawyer himself, Khan would be ideally placed to take up a role such as secretary of state for justice (although the incumbent, Shabana Mahmood, is believed to be among the most effective ministers in the current cabinet).

Starmer will not remain Labour leader forever, and it is legitimate for Khan to consider himself a viable replacement. He has won plaudits for his commitment to the green agenda and progress on social housing while standing up for London as a diverse, tolerant city in the face of provocation from right-wing populists, not least Boris Johnson and Donald Trump.

With those credentials, together with his own back story as a man from humble origins who has become the most powerful Muslim politician in Britain, many will conclude he is well positioned for a run at the leadership, should the opportunity arise.

Patrick Diamond is professor of public policy at Queen Mary, University of London, and a former government special adviser