London has the most billionaires and millionaires in the world - but they're leaving for New York

Britain's government has raised the stamp duty tax rate on the country's most expensive properties as well as slapping a foreign capital gains tax on home ownership over the last year - and now it looks like billionaires and millionaires have had enough.

They're heading to New York City.

According to a new Transatlantic Wealth Report by London-based Beauchamp Estates, New York-based Leslie J Garfield and statistical analysis by Dataloft, over the last 12 months there has been a 7% rise in London based high-net-worth investors seeking to buy prime residential property in New York.

"There has also been a 7%-10% rise in interest from London based buyers seeking luxury residential homes in Miami and Los Angeles [too]," it added.

There are now 140 billionaires and 191,000 millionaires living in London. This is more than the 103 billionaires and 389,100 millionaires living in New York.

However, the value of luxury homes in London's leading addresses are twice as high as those in Manhattan on a £/$ per square foot basis and Manhattan houses tend to be larger than those in London.

For example, the cost of a large family home in the ultra-prime location of Knightsbridge in London is on average £2,194 ($3,615) per square foot, compared to £1,196 ($1,832) per square foot on the Upper East Side (South) in Manhattan.

Beauchamp Estates and Leslie J Garfield teamed up for this report because they could see that they each need the other's help in terms of marketing and selling across both countries, since there is a change in the tide.

The world's wealthiest may dominate London at the moment but more people are looking to go to New York. There are now over 120,000 British expats living in New York City, with over 758,000 British expats living in the United States.

At the moment, there are over 197,000 American expats living in the UK, the majority of these living in Greater London or the Home Counties.

According to the report, London-based purchasers spend between £3.29 million ($5 million) to £3.95 million ($6 million) on an apartment in Manhattan. However, New York-based buyers typically spend £4 million ($6 million) to £4.1 million ($6.23 million) on an apartment or family home in London.

So, it's unsurprising seeing how the world's wealthiest may be looking to move to New York. London is more expensive to buy a property and you actually get a lot less space. Team this up with the fact that properties over the £1 million threshold are slapped with a colossal tax rate, and it's the prime time for the world's wealthiest to sell up and get out.