Nick Candy, a British property developer, attended the Abu Dhabi-led gathering and told Bloomberg, which first reported on the events: “We’re going to have the largest brain drain of talent that this country has ever seen. And they won’t come running back.”

Financial advisers have seen a spike in wealthy clients preparing to leave the UK after Labour won the general election and confirmed plans to abolish the non-dom regime, which offers generous tax breaks for expatriates.

David Lesperance, an international tax adviser, said he was “very busy” working with nom-doms who were considering relocating. He said many were making plans after hopes that Labour wouldn’t push ahead with its proposals “disappeared like morning mist in the midday sun”.

Tim Stovold, a partner at accountancy firm Moore Kingston Smith, said a “growing number of people [were] exploring options in Spain and Portugal, which both offer attractive tax regimes. The frequency and urgency of enquiries is increasing”.

Non-doms residing in the UK are currently not required to pay local taxes on overseas earnings for up to 15 years. The Government will abolish the regime next April and replace it with a time-limited grace period.

The special tax treatment has long been a source of contention because it predominantly benefits wealthy foreigners, although supporters of the tax break have argued that it keeps wealthy individuals in Britain where they then spend their money.