Artificial intelligence (AI), or the process by which computers or robots take on tasks that need human intelligence, is one of the key themes of this week's Web Summit in Lisbon.

The poll among 224 venture capitalists attending the conference showed 53 percent believed AI would destroy millions of jobs and 93 percent saw governments as unprepared for this.

The survey also found that 83 percent of the investors canvassed expect Britain's exit from the European Union to damage Europe's economy and 77 percent believe it will damage British startups.

London is widely seen as the main tech startup hub in Europe, thanks to its large pool of talent and a much bigger pool of funding than in rival centers. Cities like Berlin, Amsterdam and Lisbon are eager to attract more tech startups.

The Web Summit, one of Europe's biggest tech conferences, is being held for the first time in Lisbon, with 53,000 attendees, after moving from Dublin where it was first launched in 2010.