UNITED KINGDOM (REUTERS) - Chinese artist activist Ai Weiwei accuses Brexit Britain of being "backward".

At the UK launch of his global migration crisis film, Human Flow, Ai says the decision to leave the European Union will make the country more insular.

"I think, talk about the Brexit, policy - I think it is backward in terms of opening up globalisation and will not do Britain any good but rather to become more conservative and more exclusive and it's not a good practice or strategy," said Ai.

Prominent campaigner for the rights of child refugees, Labour peer Alf Dubs was also at the premiere to offer his thoughts.

"I think the trouble with Brexit is, you know, when the amendment first went through about child refugees I was hopeful that it would soften British attitudes towards refugees and result in people being more positive about child refugees, for a time that worked, child but then I think Brexit sent the clock back. We've got to work hard to get child refugees back high up on the agenda," said Dubs.

One of China's most high-profile artists and political activists, Ai has become a vocal campaigner on migration as the number of people forced from their homes, largely by violence and war, has reached a record 65 million.

Over a year, armed with drones, his iPhone and about 200 crew members, Ai visited more than 40 refugee camps in 23 countries to make his first feature length film which he hopes will spur people and governments to help refugees.