London's status as a global financial centre could suffer a severe blow under any Brexit deal, according to leaked government analysis of various exit scenarios.

A January paper, titled EU Exit Analysis — Cross Whitehall Briefing, found that the UK will be worse off outside the European Union under the three most likely deals, BuzzFeed News reports.

The analysis concluded that under a comprehensive free-trade agreement with the EU, UK economic growth would be 5% lower over the next 15 years compared with current forecasts. Under a no-deal Brexit, where the UK falls back on World Trade Organization agreements, that number would be 8% lower, whereas if the country remained a member of the European Economic Area, and therefore retained single-market access, growth would only fall by 2%.

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The paper also found that almost every sector of the economy and every UK region would be negatively impacted in all three scenarios, and that "there is a risk that London's status as a financial centre could be severely eroded, with the possibilities under an FTA not much different to those in the WTO option", Buzzfeed reports.

The revelations are another blow to City of London firms as it looks increasingly unlikely they will be able to negotiate some sort of continued access to the single market after Brexit. Earlier this month, French President Emmanuel Macron said that if the UK wants access, it will have to contribute to the budget and accept European jurisdiction — things that Prime Minister Theresa May has already ruled out. The EU's chief negotiator Michel Barnier has made similar remarks on several occasions.

The government document was put together by officials from various departments for the Department for Exiting the European Union and is being presented to key ministers in one-to-one meetings this week, according to Buzzfeed.

A spokesperson for the government told BuzzFeed: "We have already set out that the government is undertaking a wide range of ongoing analysis in support of our EU exit negotiations and preparations.

"We have been clear that we are not prepared to provide a running commentary on any aspect of this ongoing internal work and that ministers have a duty not to publish anything that could risk exposing our negotiation position."

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The document does not analyse a bespoke trade deal and May has repeatedly said she is seeking an "ambitious" and "comprehensive" agreement with the EU. But that has done little to allay the fears of banks, fund managers and other financial institutions in the City that rely on the single market to do business across the bloc. Many are already making — and putting into action — plans to move staff or operations to cities such as Frankfurt, Paris and Amsterdam because they cannot wait for more clarity over the final deal before adapting to potential changes.

The leak is also another embarrassment for a divided government and comes after confusion late last year over whether it had in fact commissioned its own sector-by-sector look at the impact of Brexit. After it became clear that no such analysis existed, the London Mayor Sadiq Khan commissioned his own study into how various exit scenarios would affect the city's financial and professional services sector.

In a statement this morning, Khan said: "The leaked Government analysis of the impact of Brexit clearly shows that the best way to protect jobs and growth in Britain is to remain in the single market and customs union."

He called on the government to "urgently change course" and make staying in the single market and customs union a priority.

To contact the author of this story with feedback or news, email Clare Dickinson