The warning comes after the Prime Minister accused Deloitte of “touting for business” after a leaked memo complied by the firm claimed the Government could not cope with Brexit.
David Sproul, Deloitte’s UK chief executive, made the comments after Mrs May said immigration must be tackled in the wake of the Brexit vote to show communities across the country that politicians are willing to “respond” to their concerns.
Mr Sproul said that their ability to recruit the brightest and the best from outside of the EU was vital to their success.
He told Sky News: “We have more than 100 nationalities working for us in the UK. Having a diverse workforce is vital in terms of allowing us to grow and innovate.”
Mr Sproul added that it would “definitely be possible” to adapt training for British workers if they were no longer allowed to “bring people in”.
But he insisted that it was “more likely” that they would “reluctantly” have to move current work outside the UK.
The leaked memo from Deloitte earlier this week said that an extra 30,000 civil servants may be needed to cope with the additional workload, adding that Whitehall is working on 500 Brexit-related projects.
The Prime Minister’s official spokesman said the memo was “unsolicited” and that the consultant who wrote it had not been working for the Government.
She accused Deloitte of “touting for business” and criticised both The Times and the BBC for the way in which they reported the story.