The London mayor, Sadiq Khan, has urged city leaders across the world to “build bridges instead of walls” in the wake of Donald Trump’s election, as he warned that a lack of social integration in the UK was costing the economy about £6bn.

The mayor said that uniting communities could boost economic growth in comments that will be seen as aimed at the US president-elect, who has reiterated his election promise of building a new barrier between Mexico and the US and has pledged to deport up to 3 million illegal migrants.

Khan said that pretending there was no problem with a lack of integration “for fear of losing the argument to the divisive political forces gaining pace in many countries across Europe and the world” simply would not work.



“We have seen major political upheaval around the world in recent months, with the EU referendum here in the UK and the presidential election in the US,” he said.

“This has shown how politics is becoming more and more polarised with whole communities in cities across the world feeling increasingly disconnected and estranged from national politics. That’s why now, more than ever, we need to build a strong sense of social solidarity within our cities – a renewed sense that we are united as neighbours and citizens.”

Speaking at the launch of a conference on social integration in London attended by mayors from across Europe and the deputy mayor of New York, Khan argued that migrant communities had come to live in peace and contribute, but had become increasingly concentrated in communities. He claimed that, through no fault of their own, they had become segregated.

“We need to see real leadership in cities across around the world if we are to avoid communities becoming increasingly divided,” he added. “Promoting social integration means ensuring that people of different faiths, ethnicities, social backgrounds and generations don’t just tolerate one another or live side-by-side, but actually meet and mix with one another and forge relationships as friends and neighbours, as well as citizens.”

His remarks came as images emerged of vehicles daubed with swastikas near a Jewish girls’ school in Stamford Hill, north London. Pictures posted on Twitter by the neighbourhood watch group Shomrim also showed swearwords scrawled on one van.

Shomrim said: “This was noticed this morning. The vandalised vehicles were parked opposite the entrance of a Jewish girls’ school. Young schoolchildren and their parents were shocked to discover the offensive graffiti.”

In a separate case, Nazi stickers posted on lampposts and doors were spotted in streets in Liverpool on Remembrance Sunday. Merseyside police confirmed officers were investigating.

Figures have shown a rise in race or religious hate crimes recorded by police following the EU referendum. The number of racially and religiously aggravated alleged offences logged by forces in England and Wales in July was 41% higher than in the same month last year. The number fell in August but remained higher than before the vote.