New figures reveal a massive 22 per cent fall in the number of people from the EU registering to work between 2017 and 2018 - with an even bigger 26 per cent drop in London.
Business leaders told the Standard that firms are already suffering because talented young people from European countries are choosing to work elsewhere, leading to skilled posts going unfilled.
The loss of EU talent is revealed in an analysis by City Hall of new National Insurance numbers issued to people working for the first time in the UK.
UK-wide there were 628,238 EU workers registered in the year ending in June 2016, just before the referendum, making up the vast majority of all overseas workers. In the year to June 2017 that dropped to 573,555 and then a year later it plummeted to just 443,732, a fall in one year of 22.6 per cent.
In London, the figure was 234,069 before the referendum, down to 207,179 a year later and then plunging to 152,968 - a fall of 26.2 per cent in the past year alone.
Writing in tonight’s Standard, Mayor Sadiq Khan said: “Talented people from across Europe are already deciding to take their skills and labour elsewhere ... We simply can’t afford to go on like this.”
Business organisations said the capital was being slowed down. Jasmine Whitbread, chief executive of London First, said: “Our research shows over half of London’s employers are finding it tough to hire, with fewer applications from EU citizens cited as the number one cause.
“Much of London’s success is built on the people who come to live and work here from around the world and the UK can ill afford to shut the door to global talent at a time when skills shortages are rife.
“The Government should move quickly to reassure EU citizens they are welcome and ensure the new immigration system enables business to access the skills the economy needs.”
Institute of Directors policy chief Edwin Morgan said: “At a time when skills shortages persistently rank as a top concern for employers, it’s vital that the UK represents an attractive destination for talent from across the world.”
“People from the EU play an important role in workplaces across the country, and firms would be deeply concerned to see them leave,” he said.
“The UK should seek a reciprocal preferential deal on migration with the EU as we negotiate our post-Brexit relationship, reflecting the reality of our geographical proximity and integrated supply chains.”
It included a huge 22 per cent drop in citizens from rich countries like France and Germany, and a bigger fall among eastern European citizens.