Brexit could result in the loss of nearly half a million jobs and almost £50 billion ($67 billion) in investment by 2030, according to an independent economic report published Thursday.
The analysis — commissioned by Mayor of London Sadiq Khan — models five possible scenarios for Britain's looming departure from the European Union. The scenarios range from a relatively seamless exit to leaving on World Trade Organization (WTO) terms without a transition deal, described by the study as a "hard Brexit."
The study, carried out by Cambridge Econometrics, said economic output across Britain could be around 3 percent lower by 2030 than if the U.K. were to remain within the single market and customs union — which allows the free movement of goods, people, capital and services between the member states.
Meanwhile, London's economic output would likely fall by 2 percent, the report said.
Khan said Britain could be heading for a "lost decade" of lower growth and lower employment. "Ministers are fast running out of time to turn the negotiations around," he added.
Britain and the EU will soon begin efforts to try to define their future trading relationship after officials from both sides settled the broad terms of their divorce settlement late last year.
Nonetheless, an impasse regarding Britain's access to the single market for London's substantial financial services industry is threatening to be one of the key Brexit battlegrounds before the U.K. is due to leave the bloc in March 2019.
The report said every Brexit outcome would harm the U.K. economy and "the harder the Brexit, the more severe the economic damage could be."
The worst of the five scenarios modeled, which details a departure in March 2019 with no deal or transition agreements, could lead to 482,000 fewer jobs across Britain and a loss of £46.8 billion in investment by 2030.
While the study warns of a serious impact to Britain's economy in the event of an abrupt break from the customs union and single market, the hit is notably smaller than predicted by the Treasury before the referendum. It forecast a so-called hard Brexit would prompt the U.K. economy to tank 7.5 percent by 2030, compared to 3 percent in the report published Thursday.
The calculations presented by Cambridge Econometrics are in line with assessments carried out by the International Monetary Fund (IMF) and the National Institute of Economic and Social Research (NIESR) before the referendum.