Sadiq Khan has blocked a £50m Metropolitan police deal with the controversial US tech company Palantir, sparking a bitter row between the London mayor and Scotland Yard.

After the UK’s largest police force had agreed to use Palantir’s AI technology to automate intelligence analysis in criminal investigations, Khan intervened, citing “serious concerns” about how the deal had been struck.

The mayor’s office said there had been a “clear and serious breach” of procurement rules and said police had only seriously considered one supplier (Palantir).

But after the Guardian reported the decision, Scotland Yard criticised the block as “disappointing”, saying that without new technology it would have to cut officer numbers, which would in turn affect the force’s ability to keep London safe.