The next Conservative Manifesto in 2015 will ask for a mandate from the British people for a Conservative Government to negotiate a new settlement with our European partners in the next Parliament.
It will be a relationship with the Single Market at its heart.
And when we have negotiated that new settlement, we will give the British people a referendum with a very simple in or out choice. To stay in the EU on these new terms; or come out altogether.
It will be an in-out referendum.
Legislation will be drafted before the next election. And if a Conservative Government is elected we will introduce the enabling legislation immediately and pass it by the end of that year. And we will complete this negotiation and hold this referendum within the first half of the next parliament.
It is time for the British people to have their say. It is time to settle this European question in British politics.
I say to the British people: this will be your decision.
And when that choice comes, you will have an important choice to make about our country's destiny.
I understand the appeal of going it alone, of charting our own course. But it will be a decision we will have to take with cool heads. Proponents of both sides of the argument will need to avoid exaggerating their claims.
Of course Britain could make her own way in the world, outside the EU, if we chose to do so. So could any other Member State.
But the question we will have to ask ourselves is this: is that the very best future for our country?
We will have to weigh carefully where our true national interest lies.
Alone, we would be free to take our own decisions, just as we would be freed of our solemn obligation to defend our allies if we left NATO. But we don't leave NATO because it is in our national interest to stay and benefit from its collective defence guarantee.
We have more power and influence - whether implementing sanctions against Iran or Syria, or promoting democracy in Burma - if we can act together.
If we leave the EU, we cannot of course leave Europe. It will remain for many years our biggest market, and forever our geographical neighbourhood. We are tied by a complex web of legal commitments.
Hundreds of thousands of British people now take for granted their right to work, live or retire in any other EU country.
Even if we pulled out completely, decisions made in the EU would continue to have a profound effect on our country. But we would have lost all our remaining vetoes and our voice in those decisions.
We would need to weigh up very carefully the consequences of no longer being inside the EU and its single market, as a full member.
Continued access to the Single Market is vital for British businesses and British jobs.
Since 2004, Britain has been the destination for one in five of all inward investments into Europe.
And being part of the Single Market has been key to that success.
There will be plenty of time to test all the arguments thoroughly, in favour and against the arrangement we negotiate. But let me just deal with one point we hear a lot about.
There are some who suggest we could turn ourselves into Norway or Switzerland - with access to the single market but outside the EU. But would that really be in our best interests?
I admire those countries and they are friends of ours - but they are very different from us. Norway sits on the biggest energy reserves in Europe, and has a sovereign wealth fund of over 500 billion euros. And while Norway is part of the single market - and pays for the principle - it has no say at all in setting its rules: it just has to implement its directives.
The Swiss have to negotiate access to the Single Market sector by sector. Accepting EU rules - over which they have no say - or else not getting full access to the Single Market, including in key sectors like financial services.
The fact is that if you join an organisation like the European Union, there are rules.
You will not always get what you want. But that does not mean we should leave - not if the benefits of staying and working together are greater.
We would have to think carefully too about the impact on our influence at the top table of international affairs. There is no doubt that we are more powerful in Washington, in Beijing, in Delhi because we are a powerful player in the European Union.
That matters for British jobs and British security.
It matters to our ability to get things done in the world. It matters to the United States and other friends around the world, which is why many tell us very clearly that they want Britain to remain in the EU.
We should think very carefully before giving that position up.
If we left the European Union, it would be a one-way ticket, not a return.
So we will have time for a proper, reasoned debate.
At the end of that debate you, the British people, will decide.
And I say to our European partners, frustrated as some of them no doubt are by Britain's attitude: work with us on this.
Consider the extraordinary steps which the Eurozone members are taking to keep the Euro together, steps which a year ago would have seemed impossible.
It does not seem to me that the steps which would be needed to make Britain - and others - more comfortable in their relationship in the European Union are inherently so outlandish or unreasonable.
And just as I believe that Britain should want to remain in the EU so the EU should want us to stay.
For an EU without Britain, without one of Europe's strongest powers, a country which in many ways invented the single market, and which brings real heft to Europe's influence on the world stage which plays by the rules and which is a force for liberal economic reform would be a very different kind of European Union.
And it is hard to argue that the EU would not be greatly diminished by Britain's departure.
Let me finish today by saying this.
I have no illusions about the scale of the task ahead.
I know there will be those who say the vision I have outlined will be impossible to achieve. That there is no way our partners will co-operate. That the British people have set themselves on a path to inevitable exit. And that if we aren't comfortable being in the EU after 40 years, we never will be.
But I refuse to take such a defeatist attitude - either for Britain or for Europe.
Because with courage and conviction I believe we can deliver a more flexible, adaptable and open European Union in which the interests and ambitions of all its members can be met.
With courage and conviction I believe we can achieve a new settlement in which Britain can be comfortable and all our countries can thrive.
And when the referendum comes let me say now that if we can negotiate such an arrangement, I will campaign for it with all my heart and soul.
Because I believe something very deeply. That Britain's national interest is best served in a flexible, adaptable and open European Union and that such a European Union is best with Britain in it.
Over the coming weeks, months and years, I will not rest until this debate is won. For the future of my country. For the success of the European Union. And for the prosperity of our peoples for generations to come.