Rutger Bregman, journalist and author of Utopia for Realists, told Business Insider that borders are a barrier to equality worldwide.
He said: "
Just take for example someone who lives in Nigeria and has exactly the same skill set, the same education as someone who lives in the UK or the US, but they earn about 8 times less.
"So the right passport is worth a lot of money. It's a huge source of global inequality.
"We've got a mountain of economic research that shows that immigration is the most powerful weapon we have in the fight against global poverty.
"Immigration in all of our history is one of the most powerful drivers of prosperity and we should never forget that."
Produced by Joe Daunt. Filmed by David Ibekwe. Special thanks to Will Martin and Alana Kakoyiannis