Crime-busting former New York Mayor Rudy Giuliani has said London Mayor Sadiq Khan “should be ashamed of himself” for spending his time denigrating President Donald J. Trump while “crime is spiralling” in his city.

“Sadiq Khan should be ashamed of himself,” the political veteran told Britain’s Sunday Express.

“He’s so busy attacking President Trump’s visit and, in the meantime, crime is spiralling in London. Maybe he should just do his job instead of attacking a world leader.”

The heavyweight Republican spoke after Khan’s decision to authorise a giant balloon depicting the President as an orange baby in a nappy to fly over the British capital during his visit to the country later this week. Khan has been a highly vocal critic of Trump both during his presidency and during the presidential campaign, repeatedly calling for the visit to be cancelled.

The leftist mayor suggested respect for freedom of expression and peaceful protest were behind the balloon decision, although Khan has not always been such a free speech warrior — pouring over £1.7 million into an “online hate crime hub” to police mean comments on the internet at a time when the police are struggling to cope with a violent crime wave and leaving many burglaries uninvestigated, for example.

Murder Surges 44 Per Cent in Khan’s London Amidst ‘Troubling’ Rise in Serious Crime https://t.co/lM2ewca1Z5 — Breitbart London (@BreitbartLondon) May 20, 2018

Giuliani warned that Khan’s constant attacks on President Trump — who has been one of Britain’s few genuine friends and supporters abroad since the Brexit vote — could damage the historic British-American friendship, and even undercut the tourist trade.

“Many people who come to London are Americans. More than half of us in the U.S. now support the President and even those who don’t support him, support his office,” he observed.

“I would not like to go to a country where someone with the authority of a mayor was rallying people against them. It’s highly inappropriate. He’s probably suffering from some of the criticisms that President Trump has made of him, which are valid,” he added.

“If crime is going up, he’s obviously not paying attention to his job. This is one mayor who can tell him how to reduce crime – you have to pay attention to your job. From one mayor to another – do your job, Mr Khan.”

Trump: "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is "no reason to be alarmed!" https://t.co/ESfgEPOYpV — Breitbart London (@BreitbartLondon) June 4, 2017

Giuliani cut crime in New York City substantially during his time in office, implementing the ‘broken windows’ model of policing which sees the authorities tackle low-level crime and disorder robustly, in the belief that the results will cascade upward.

This diverges markedly from the approach of the Metropolitan Police in London under Khan’s oversight, with police leaders suggesting that investigating many low-level crimes is “not practical” and that they will increasingly not bother doing so in many cases.

Follow Jack Montgomery on Twitter: @JackBMontgomery