Arm CEO Simon Segars. Albert Gea / Reuters Simon Segars — the CEO of Britain's biggest tech company Arm Holdings — has warned that a hard brexit could seriously damage his business, in an interview with The Financial Times. The Cambridge-headquartered company designs microchips for a variety of smartphones including Apple's iPhone.

Segars said, “There are a finite number of [UK] engineers with the right skills we can hire...we have 300 people in Cambridge right now from mainland Europe, and more could start tomorrow. If there was some law enacted that said every employee has to be from the UK, the business would fail,” he warned.

It's his first interview since Arm was acquired by Japan's Softbank in July of this year — the largest ever acquisition of a European technology business. When the acquisition was confirmed, Softbank said it intended to remain headquartered in Cambridge and expected Arm's 3,000-strong workforce to at least double in size over the next five years.

Segar's warnings come on top of concerns that Britain lost its biggest tech company to Japan at the time of the acquisition. Chancellor Phillip Hammond endorsed the sale in a statement that read: "Just three weeks after the referendum decision, it shows that Britain has lost none of its allure to international investors. Britain is open for business — and open to foreign investment." He added: "Softbank’s decision confirms that Britain remains one of the most attractive destinations globally for investors to create jobs and wealth. And as ARM’s founders will testify, this is the greatest place in the world to start and grow a technology business."

But the sale concerned some people, including one of the cofounders of ARM. Hermann Hauser told the BBC on the days the news of the sale broke that it was "a sad day for me and for technology in Britain".

Other UK technology companies have spoken out against the impact of a so-called "hard Brexit" and the tightening of immigration rules that could come with it. A poll of tech startups before the referendum found that 87% of respondents were opposed to Brexit. And Jason Trost, CEO of betting startup Smarkets, told Business Insider in September that his company was planning to expand in the US rather than the UK following the referendum.