In a speech last weekend, the Prime Minister rightly restated Britain’s unconditional commitment to the security of Europe, regardless of Brexit. She outlined a vision of a future security partnership to deliver this commitment.

But Theresa May’s proposals are based on a fundamental misunderstanding of the nature of the EU’s ongoing defence integration. They would leave the UK in an unacceptable position as a subordinate to a protectionist European Defence Union.

Over the past 18 months, British and European officials in nearly all policy areas have been working out how best to detach the UK from the EU. Perversely, the opposite has been the case in the area of defence. Since November 2016, the UK has joined all parts of the EU’s Defence Union – except one. The UK was one of 3 Member States to opt out of Permanent Structured Cooperation (PESCO), but involvement in all the other mechanisms will keep Britain attached. The complex web of programmes covers finance, procurement rules and command centres. Unbelievably, this has all happened without a vote in Parliament, and little or no press coverage explaining what is going on behind our backs.

The Government says it wants to participate in schemes – including the European Defence Fund, the European Defence Industrial Programme and the European Defence Agency – even after we have formally left the EU in March 2019. In Munich, Theresa May confirmed her vision included UK deployment of our “significant capabilities and resources with and indeed through EU mechanisms”. But who is choosing which mechanisms are of benefit to Britain and which are not? With a recent change of Defence Minister, this has become even more confusing. What is happening at the moment, behind closed doors is worrying.

Involvement in these programmes will generate significant risks for Britain. We will still be subject to continued payments into Brussels’ coffers. Membership of the emerging Single Market in Defence could require oversight by the European Court of Justice, contradicting Mrs May’s commitment to take us out of the ECJ’s jurisdiction. Thirdly, despite EU claims to the contrary, these programmes will inevitably cause duplication with NATO. Concerns about duplication were expressed in Munich by the NATO Secretary General, Jens Stoltenberg, as well as by American officials. It is also unclear how committed the Remaining 27 EU Member States will be on an ongoing basis to NATO. Only Romania, Greece, Estonia and Poland meet the NATO spending target of 2% of GDP. Meanwhile, Germany only manages 1.1%.

How has Britain ended up in this paradoxical position of integration in EU defence while leaving the EU? Partly it is a result of lobbying by self-serving UK defence companies who have been on the receiving end of a charm offensive by EU mandarins – with clear promises of future procurement deals.

Another explanation is the complicated and often dishonest manner of the EU’s drive to integrate. MPs and even ministers – let alone the public – do not seem to be fully aware of the consequences of the convoluted system.

This combination of misunderstandings and deception has been a hallmark of British involvement in the EU from its very beginnings.

The Prime Minister’s recent remarks in Munich exemplify this misconception. Despite talking up British participation in aspects of the Defence Union – she spoke of the need for an “independent foreign policy”, of a “sovereign United Kingdom”. The trouble is, as Britain has so often found as a member of the EU, it is impossible to be in the aspects we like, without the inherent political obligations. Put another way, there can be no cherry-picking.

Mrs May’s words reflected the desire of UK officials to be at the top table with an influence on policy. Belief in this desire ignores the reality of significant divergence in views on defence between the UK and the EU. Our two main goals in this sphere in recent years has been to prevent duplication with NATO and prevent protectionism of defence industries. The detail behind the EU’s defence mechanisms exposes our comprehensive failure in these aims.

On many occasions, the UK has become integrated with the EU by the back door, without MPs, officials or the public being fully aware of the ramifications. This is clearly now happening with defence, and we must not allow it.

If we are to fully regain our sovereignty, it is essential we get Britain out of the EU’s Defence Union, and we will only cooperate with the EU on defence on an independent, case-by-case basis.

Peter Lyon is a Research Executive at cross-party grassroots campaign Get Britain Out