It says member states “shortchanged” their own defence by nearly £340 billion between 2012 and 2016.

But the UK has propped up the protection of Europe by £17billion over the same period, according to the Henry Jackson Society think-tank.

Its report, What the European Union owes the United Kingdom, says our military contribution should be taken into account in talks about the Brexit divorce bill.

Last month chief European Commission negotiator Michel Barnier infuriated many MPs by claiming Britain was abandoning the EU’s fight against Islamic State.

EU leaders are also committed to creating a European Army, a move the UK has resisted for fear it would undermine Nato.

We are one of only five Nato members to meet the alliance’s spending target of two per cent of GDP, alongside the US, Greece, Estonia and Poland.

The HJS says EU states that failed to meet the two per cent Nato target include wealthy Germany, which underspent by £106billion, Italy (£67billion), Spain (£56billion) and France (£18billion).

Its report says: “European defence is substantially dependent upon the United Kingdom’s financial contribution.

“Countries that are members of both Nato and the EU shortchanged the alliance and therefore their own security.”

It adds that the figures are a “pertinent reminder” to Brussels of Britain’s unwavering commitment to European defence security.

And it warns the EU will almost certainly need British military support in the future – so should ensure the new relationship does not “descend into mutual acrimony”.