When Britain finally leaves the European Union, the bloc will face a budget shortfall of up to €15 billion a year.

The current EU budget period ends in 2020, about the time that the proposed Brexit transition period is likely to finish, and ran to about €960 billion (about £849 billion) from its start in 2014. Almost 75 per cent of that cash went on agricultural subsidies and developing poorer EU countries.

The next budget or “Multi-annual financial framework” will run for at least five years from 2021 and be without payments from Britain, one of the major net contributors to Brussels’ coffers. A net contributor pays more into the budget than it receives in EU funding.

While the total figure is subject to traditionally torturous negotiations between national governments and the European Parliament, the budget usually works out at about €150 billion (£133 billion) a year.

The European Commission has vowed that it will not rely on debt to finance EU spending, meaning that every euro has to be found from existing or new revenue streams.

Further complicating matters, the commission has said that it will need to find about another €10 billion (£8.85 billion) for EU programmes on defence, migration and the EU’s border agency.