Boris Johnson warns low immigration could stall economic growth

Mayor of London warns of the dangers of low immigration - a week after Conservative leadership rival Theresa May said net impact of mass migration was 'close to zero'

Boris Johnson is on a trade trip to Japan (PA)

Boris Johnson has warned that low levels of immigration could lead to economic stagnation as he deepened government divisions over controlling migration.

The Mayor of London, on a visit to Tokyo, pointed to Japan's falling population as a factor behind its lack of economic growth in recent years and said it was something that Britain "might think about" in efforts to curb the number of people arriving from overseas.

His comments come a week after Theresa May delivered the most hard-line speeches from a Home Secretary in recent times as she claimed mass migration to the UK threatened social cohesion and said the net impact of immigration was "close to zero".

Mr Johnson was quick to distance himself from her approach and his sister, Rachel Johnson, said she was "depressed" and "shocked" by the speech.

Speaking on a trade trip to Japan, Mr Johnson said: “They have been going through a long period of stagnation but they are hoping to pull out of it.

"They have got demographic problems. One of the questions that people in Britain might think about is obviously that they have very, very low immigration and very, very low, in fact negative, population growth, they have got a shrinking population.

“That has, of course, contributed to the long period of economic stagnation they are going through, but that has got to be seen in context. This is still an amazing, dynamic, vibrant, fantastically rich economy, the third biggest in the world and we have got to be here.”