London Mayor Sadiq Khan. (File photo/REUTERS)

Khan based his statement on a report he commissioned from economic consultants Cambridge Econometrics, who estimated how fast the economy would have grown if Britain had voted to stay in the EU.

It's now obvious that Brexit isn't working, he said, adding  “The hard-line version of Brexit we've ended up with is dragging our economy down and pushing up the cost of living.”

Cambridge Econometrics said Brexit was expected to lower annual economic growth in Britain by 0.4 percentage points between now and 2035, lower employment levels by 3 million by 2035 and reduce investment by a third.