New York is bracing for an “exodus of billionaires” after the Democrats nominated a staunch socialist as their candidate for mayor.

Zorham Mamdani, a 33-year-old “anti-Zionist”, sent shock waves through American politics on Tuesday when he beat Andrew Cuomo, the former governor, in the Democratic primary, earning him the party’s nomination for November’s mayoral election.

A rank outsider, Mr Mamdani was carried to victory by a wave of young voters who were won over by his radical campaign pledges to freeze rents and introduce free public transport and city-run grocery stores, all of which he pledged would be paid for by hiking taxes on the wealthy.

The primary result has sparked panic among New York’s ultra-rich, with luxury real estate agents inundated with calls from clients looking to relocate or freeze plans to move their businesses to Manhattan.

One high-end broker described Mr Mamdani’s victory as the “worst thing for the housing market since 9/11”, while another called it the “nail in the coffin” for New York.

“There’s an old saying in real estate: Money goes where it’s welcome,” said John Boyd Jr, founder of Florida-based corporate site selection specialist The Boyd Co, who works with a range of multi-millionaire New York-based clients.

“There’s alarms going off among many key executives as well as the billionaire class about New York becoming a socialist run city,” he said.