Damian Green is a former Immigration and Policing Minister, and is MP for Ashford.

We have recently seen one referendum produce the right result, but only after some significant wobbles along the way. There is another referendum coming, which is just as important for the future of the United Kingdom, and it is never too early to start making the argument for Britain’s place in the European Union.

At this conference it is important to go further. We Conservatives must make the Conservative case for our membership. We must not allow the distorted view that pro-European Conservatives are a tiny minority to go unchallenged. Because it’s false, it’s damaging to the Party, and it’s put about by those who know it’s false, but who hope to make it come true by repeating it as often as possible.

The vast majority of the party, inside and outside Parliament, agree that Europe needs reform. We want David Cameron to succeed in his negotiations after the election and lead the campaign to keep us in, and to put this question to bed for at least another generation.

Why do I think it’s damaging? Because one of the interests the Conservative should always take seriously is the business interest—the people who create jobs and prosperity for everyone.

Overwhelmingly, the serious voices in British business want us in. The CBI, the IOD, the Engineering Employers, want us in. Ford, BAe, Unilever, Citibank, Siemens, have all warned about the damage that would be caused to their businesses and tens of thousands of their workers if we pulled out.

It is true that the fastest-growing economies in the world are countries like India and China in other parts of the globe. But I have never understood why it making it more difficult to export to Germany makes it easier to export to China.

Furthermore, the EU has a leverage in trade negotiations that far exceeds that of any individual member state. Agreements such as the Transatlantic Trade and Investment Partnership are vital. This historic deal would allow free trade between the EU and the US, economies that account for nearly half of global output and a third of trade flows. This is central to our vision of a reformed competitive Europe.

Leaving the economic reasons for a moment, membership of the European Union also benefits the UK in a number of other areas.

First in terms of security. Membership of the European Union plays a fundamental part in tackling terrorism and organised crime. The European Arrest Warrant (EAW) ensures, through police coordination, that criminals cannot hide in Europe, as well as ensuring that the UK can extradite criminals wanted in other EU countries. Over the last two years, the UK has used the EAW to extradite at least 71 non-UK nationals suspected of committing serious crimes in the UK. The EAW has also been used to arrest and return 51 (out of 65) of the most wanted British nationals on the run in Spain. Our police are absolutely right to argue that we need to keep the European Arrest Warrant.

More widely, given the current state of the world, what would we be thinking about in turning away from our closest neighbours? Are so we confident of a friendly reception in other parts of the world that we can turn to 27 other friendly democracies and say we don’t want to be part of a club with you any more. Is that going to increase our influence in the world, or damage it? Would it make it more or less likely to encourage the US President to pick up the phone to Downing Street in a crisis? Would it make the Indians and Chinese take us more seriously as trading partners, or dismiss us a bunch of nostalgic eccentrics?

Instead, we need to play a leading role in reforming Europe, not just for our benefit, but the benefit of all European citizens. We need to focus Europe on its most important tasks, and make the institutions more democratic. This is in Britain’s vital national interest.

The EU is built upon fundamental principles such as the respect for the rule of law, human rights, democracy, free markets, pursuing self-improvement and offering solidarity. The very things that the British stand for.

One lesson we must learn from the Scottish Referendum is that although it is vital to win the economic argument it is also important to win the emotional arguments. We need to engage heads and hearts. And there is an idealistic vision of a continent that spend centuries tearing itself apart with wars that destroyed communities and whole countries, which in the last 70 years has become a haven of peace and prosperity, and which has built that peace and prosperity in countries that had previously known nothing but occupation and oppression. Go to Cracow, go to Bucharest, go to Vilnius and see what they think. Britain can be proud of our part in building this peaceful and prosperous continent.

In the previous referendum in 1975, some wise words were spoken. “The choice is clear. We can play a role in developing Europe or we can turn our backs on the Community. By turning our backs we forfeit our right to influence what happens in the Community. But what happens in the Community will inevitably affect us.”  That was right when Margaret Thatcher first said it, and it is still right today.  For the sake of the Conservative Party, and for Britain’s sake, we need to make that argument every day from now until 2017.