Donald Trump is a 'vulgar, demented, pig demon' who only appeals to 'emasculated' middle-aged men, the former innovation adviser to Hillary Clinton has said.

Alec Ross, who was senior aide to Clinton during her term as Secretary of State, was speaking at The Hay Festival in Wales about the industries of the future.

Ross, said that the most open countries would have the greatest success in the coming decades because the biggest emerging markets were big data and genomics. But he warned that America could become a more closed society if Donald Trump was elected president.

"We're having this struggle very publicly in the United States right now where a vulgar, demented, pig demon named Donald Trump is trying to make the United States a more closed society.

"We'll be saying, no more brown people, no more Muslims, let's get women back in the kitchen. Let's make America great again.

"What he's talking about is taking emasculated men in their forties, fifties and sixties who are not living the life they hoped for in their teens and twenties and saying, 'you know what? there are people to blame for this. And we're going to build a wall and we're going make America great again.

"At the core of that is the struggle between being an open society and a closed society. And so if you want to know where the trillions of dollars of wealth creation that are going to come with the commercialisation of genomics, and the creation of big data companies, and the AI machine learning companies and all of the industries of the future my overarching line here is it's going to be the most open societies.