You are on the verge of losing your greatest ever ally – and I felt moved enough by this fact to visit your country’s capital this week, a trip which I have very much enjoyed.

I’m very grateful to the Heritage Foundation for providing myself and a group of European politicians with a platform, it is clear that the think tank community in Washington, D.C. is alive and well, and absolutely dwarves anything that now exists in London.

I came on this trip with a very specific and direct message. We have in our sights a referendum on Britain’s membership of the European Union. Something my party has been fighting for 22 years against the political establishment for. This vote will directly affect the United States’s “special relationship” with their best ally – the United Kingdom –and I urge you all to pay great attention to the debate over the coming months, because this will be written about in history books for decades if not longer. Especially if we fail.

Way back in the early 1960’s, America’s Central Intelligence Agency (CIA) and other US government bodies were very keen to get the United Kingdom into what was then called the European Economic Community (EEC). This is hardly a surprise, given the huge cost in both human and financial terms that it took to win the Second World War. And the U.S. still had half a million men on European soil to maintain the peace – a massive undertaking.

So to Washington, and U.S. leaders, the idea of a peaceful Europe coming together with a strong British influence at the centre was very appealing. But much has changed in the last fifty years. The EEC has morphed into a political project, not an economic union, and is now called the European Union (EU). The EU now has its own flag, its own anthem and its very own ‘President’, not that anybody knows his name.

Much of what the EU does today is divisive, not unifying. In the case of Greece, and the Euro, it is not just dividing people, but also failing in a spectacular fashion.

And yet the record that is placed by the U.S. State Department never changes. Even the International Monetary Fund based in Washington, D.C. now appears to be a branch office of the European Commission, and your President Obama is the biggest pro-EU cheerleader that the U.S. has ever produced. This latter endorsement ought to tell you all you need to know about the European project.

I think part of the problem today is that too many in America think the EU is a bit like the North American Free Trade Agreement (NAFTA). It isn’t. And there has always been a lack of debate and voices coming from Washington politicians to identify the real nature of this supranational form of government.

This week, I appeared on Fox Business, and was faced with a former Goldman Sachs employee, a retired General who thought Euro exit would mean Greece leaving NATO, and somebody who purported to be a Greek businessman who argued that the Euro was good for Greece.

It was an interesting, hour-long interview, and whilst the discussion continued we had live footage of Molotov cocktails exploding outside the Greek Parliament in the background.

But it does seem to me that almost every commentator in Washington unanimously agrees with statement: “EU good, Euro good”. I am here to urge American politicians and commentators to think again.

The United Kingdom is, and has for many years been the best partner and ally that you have in the world. But if we vote ‘Yes’ in our upcoming referendum – on the question, should Britain remain a member of the European Union – then our ability to be that ally will diminish.

The EU now has a high representative for foreign affairs. It has established over 150 proto-Embassies around the world. In many areas such as Africa and Russia, the United Kingdom no longer has a foreign policy but speaks as part of an EU voice.

A British ‘Yes’ vote will lead to a further depending of the EU foreign policy agenda, and restrict our freedom to make up our own minds and to act with traditional allies. Indeed as you once achieved independence from Britain, we are fighting for our independence, our sovereignty, our rights back from Brussels.

Then, there is the military dimension.

Yes we have been part of NATO and worked closely together for nearly 70 years, but the European Union wants to develop its own army, air force and navy. When I raised this point with then Deputy Prime Minister Nick Clegg in 2014 he described my comments as a “dangerous fantasy“. But the truth is the EU navy is already active in a role to contain the Somali pirates, and there are EU military missions all over the world.

Indeed, EU Commission President Jean Claude-Juncker has stated in the last few weeks that he wants a European Army and a command and control structure has already been set up in Brussels. Some in the British government, especially many in the Treasury, seem to think this is good news at it means we can continue to cut our military expenditure and therefore our capability, because we can rely on our EU colleagues to help us out.

A British ‘Yes’ vote will lead to deeper military integration and activity, and a reduced Anglo-American influence. The emergence of this EU army indeed directly threatens the continued existence of NATO.