Another 18 shopping centres like Brent Cross are needed in London

Economic group Experian said the huge increase would be needed on top of schemes already planned for the city.

The study for the Greater London Authority (GLA) said London's increasing population will lead to 4.8% rise in spending.

The report also said Westminster is the most "shop-deficient" borough.

High street development

The report is based calculations on an extra one million people living in the city.

Dr Neil Blake, retail economist for Experian, told BBC London: "There probably isn't enough space for another Brent Cross in the centre of London.

"We can't keep on increasing the West End forever. But there are under-developed high streets and neighbourhood centres which could be developed."

He said without the growth, Londoners may become "disillusioned" and shop elsewhere and it would be detrimental to tourism.

'Good experience'

Westminster Councillor Michael Vearncombe disagreed with claims that his borough was "shop-deficient".

"We are well served. We want to be able to offer a variety of shopping experiences so that everyone that comes to the city feel that they have a good experience," he said.

The GLA commissioned the study to help future planning decisions.

Central London and the south of the city were most in need of extra space, according to the study.