The 28-year-old investor said: “Every single day, I am getting calls from founders looking at moving to another country. They are saying, ‘I don’t know why I would build a business in the UK.’
“This is not the rich, this is ambitious, young founders building a business from nothing.”
Officials are believed to be considering scrapping Business Asset Disposal Relief, also known as entrepreneurs’ relief, which allows founders to reduce their tax bill when selling companies.
Seb Wallace, co-founder of Triple Point Ventures, warned that “any move to increase capital gains tax for business owners, without a material increase in Business Asset Disposal Relief, risks a flight of talent out of the UK”.
“It is something we hear many founders talking about,” he added.
Last month, 11x, the artificial intelligence start-up, announced it had moved its headquarters from the UK to San Francisco, on the back of raising $24m from largely US venture capitalists.
More than 1,000 entrepreneurs have signed a letter to the Chancellor warning that raising capital gains taxes would reduce the incentives that people have to start businesses.
A Treasury spokesman said: “We do not comment on speculation around tax changes outside of fiscal events.”