France and Germany risk starting a new financial crisis if they try to use Brexit to dismantle the London-based heart of the global economy “just to make a political point,” one of the City’s most senior figures has warned.

Xavier Rolet, chief executive of the London Stock Exchange Group, says European leaders who demanded tighter global regulation after the 2008 financial crisis are now threatening to “fragment” those same standards to punish Britain for Brexit.

Writing for The Telegraph, Mr Rolet calls on the Bank of England and regulatory bodies in Europe to speed up talks on regulation to ensure that the carefully constructed system of global regulation developed to stop unexpected risks emerging does not collapse.

He calls for an "update" on the progress of these talks to reassure international financial firms.

The head of the stock market uses the article to welcome Theresa May's call for a transition period to give business certainty but said that the details must now be agreed before the end of the year. British jobs will begin relocating abroad next year if the uncertainty continues, he warns.

His intervention came as it emerged that Germany is secretly working on proposals for a “comprehensive free trade accord” with Britain. There is also evidence that Brussels is prepared to begin talks within the EU over what a future round of trade discussions may look like - but it will not agree to formal negotiations beginning.