Pro-EU George Osborne has admitted failures in the European Union (EU) after conceding 3.3million immigrants would arrive in Britain if we vote to remain in the bloc.

Britain should expect to take in enough immigrants to fill a new city more than six times the size of Leeds if we vote to stay in the EU in the June 23 referendum.

The startling revelation, buried deep in a lengthy Treasury report on the economic impact of Brexit, would mean the UK’s population would reach 71.4m in 14 years.

Senior Treasury officials said they expect the current record net number of 329,000 new arrivals a year will fall to 185,000 by 2021 and continue at that rate after.

The admission means he agrees the Conservative’s election promise to reduce immigration to tens of thousands annually will be broken for a second time.

The forecast was made by the independent Office of National Statistics in October last year, but this is the first time it has been formally backed by ministers.

A senior Tory said Mr Osborne should be ashamed of himself for the report while another said Project Fear – the Brexit camp’s name for the Remain campaign – had turned into “Project Utter C**p”.