I want to be explicit. Yes, the British people voted to leave Europe. And I agree the will of the people should prevail. I accept right now there is no widespread appetite to re-think. But the people voted without knowledge of the terms of Brexit. As these terms become clear, it is their right to change their mind. Our mission is to persuade them to do so.

What was unfortunately only dim in our sight before the referendum is now in plain sight. The road we're going down is not simply Hard Brexit. It is Brexit At Any Cost. Our challenge is to expose relentlessly what this cost is, to show how the decision was based on imperfect knowledge which will now become informed knowledge, to calculate in ‘easy to understand’ ways how proceeding will cause real damage to our country; and to build support for finding a way out from the present rush over the cliff’s edge. I don't know if we can succeed. But I do know we will suffer a rancorous verdict from future generations if we do not try.

How hideously, in this debate, is the mantle of patriotism abused. We do not argue for Britain in Europe because we are citizens of nowhere. We argue for it precisely because we are proud citizens of our country – Britain – who believe that in the 21st Century, we should maintain our partnership with the biggest political union and largest commercial market on our doorstep; not in diminution of our national interest, but in satisfaction of it.

Consider for a moment the surreal situation in which our nation finds itself. I make no personal criticism of the PM or the Government. I know the PM is someone who cares about our country, who is trying to do the right thing as she sees it, and I know how demanding the job of leadership is.

But just consider: nine months ago both she and the Chancellor, were telling us that leaving would be bad for the country, its economy, its security and its place in the world. Today it is apparently a ‘once in a generation opportunity’ for greatness. Seven months ago, after the referendum result, the Chancellor was telling us that leaving the Single Market would be – and I quote – ‘catastrophic’. Now it appears we will leave the Single Market and the Customs Union and he is very optimistic.

Two years ago the Foreign Secretary was emphatically in favour of the Single Market. Now ditching it is ‘brilliant’. The PM says she wants Britain to be a great open trading nation. Our first step in this endeavour? To leave the largest free trading bloc in the world. She wants Britain to be a bridge between the EU and the USA. How to begin this worthy undertaking? To get out of Europe thus leaving us with no locus on the terrain where this bridge must be constructed.

We are told that it is high time our capitalism became fairer. And how do we start laying the foundation for such a noble cause? By threatening Europe with a move to a low tax, light regulation economy, the antithesis of that cause. This jumble of contradictions shows that the PM and the Government are not masters of this situation. They're not driving this bus. They're being driven. And as we pass each milestone so the landscape, in which we are operating, changes not because we have willed the change, but because this is the direction in which the bus is travelling. We will trigger Article 50 not because we now know our destination, but because the politics of not doing so, would alienate those driving the bus.

The surreal nature of the exercise is enhanced by the curious absence of a big argument as to why this continues to be a good idea. Many of the main themes of the Brexit campaign barely survived the first weekend after the vote. Remember the £350m a week extra for the NHS? Virtually the only practical arguments still advanced – under the general rubric of ‘taking back control’ – are immigration and the European Court of Justice.

On the ECJ, I would defy anyone to be able to recall any decisions which they might have heard of; as opposed to the decisions of the European Court of Human Rights, a non-EU body. I can honestly say that during all my time as PM there was no major domestic law that I wanted to pass which Europe told me I couldn't. It is true ECJ rulings are important on technical issues. Some business likes; some not. But no one would seriously argue that the ECJ alone provides a reason for leaving Europe.

Immigration is the issue. Net immigration into the UK was roughly 335,000 in the year to June 2016. But just over half was from outside the EU. I know, in some parts of the country, there is a real concern about numbers from Europe and the pressures placed on services and wages.

However of the EU immigrants, the PM has recently admitted we would want to keep the majority, including those with a confirmed job offer and students. This leaves around 80,000 who come looking for work without a job. Of these 80,000, a third comes to London, mostly ending up working in the food processing and hospitality sectors. It is highly unlikely that they're ‘taking’ the jobs of British born people in other parts of the country. The practical impact of Brexit on immigration is on analysis less than 12 per cent of the immigration total. And for many people, the core immigration question – and one which I fully accept is a substantial issue -is immigration from non-European countries, especially when from different cultures in which assimilation and potential security threats can be an issue.

Yet this impacted the Brexit decision. It was Donald Trump who said without the refugees from Syria, ‘you probably wouldn't have a Brexit.’ It is no coincidence that the infamous immigration poster of Leave was a picture of Mr Farage in front of a line of Syrian people. Thus, we have moved, in few months, from a debate about what sort of Brexit, involving a balanced consideration of all the different possibilities; to the primacy of one consideration – namely controlling immigration – without any real discussion as to why and when Brexit doesn't affect the immigration people most care about.

Now we're told we have to stop debating Brexit and just do it. Frankly, I would question whether the referendum really provides a mandate for Brexit At Any Cost. But suppose that it does. The argument is then that the British people have spoken; we must deliver their will; and we should just ‘get on with it’. I agree ‘getting on with it’ is a very powerful sentiment, at present the predominant sentiment.

But were we to be true to the concept of Government through British Parliamentary democracy, rather than Government by one-off plebiscite, we would also feel obliged to point out that it isn't a question of just ‘getting on with it’. This is not a decision that once made is then a mere matter of mechanics to implement. It is a decision which then begets many other decisions. Every part of this negotiation from money to access to post Brexit arrangements is itself an immense decision with consequence. If we were in a rational world, we would all the time, as we approach those decisions, be asking: why are we doing this and as we know more of the costs, is the pain worth the gain?

Let us examine the pain. We will withdraw from the Single Market which is around half of our trade in goods and services. We will also leave the Customs Union, covering trade with countries like Turkey. Then we need to replace over 50 Preferential Trade Agreements we have via our membership of the EU; for instance with Switzerland. So, EU-related trade is actually two thirds of the UK total. This impacts everything from airline travel, to financial services to manufacturing industry, sector by sector.

We will pay for previous EU obligations but not benefit from future opportunities, with figures as high as £60bn as the cost. We will lose influence in the world’s most significant political union; and have to negotiate on our own on issues like the environment where we presently benefit from Europe’s collective strength. There is alarm across sectors as diverse as scientific research and culture as European funding is withdrawn. And all this then to do an intricate re-negotiation of the trading arrangements we have just abandoned.

That negotiation is without precedent in complexity. It is even possible that it fails and we end up trading on WTO rules. This is in itself another mine field: we would need to negotiate the removal not just of tariff barriers; but the prevention of non-tariff barriers which today are often the biggest impediments to trade and pile costs on business.

This could take years. Our currency is down around 12 per cent against the Euro and 20 per cent against the dollar, which is the international financial market’s assessment of our future prosperity i.e. we are going to be poorer. The price of imported goods in the supermarkets is up and thus the cost of living. Of course Britain can and would survive out of the EU. This is a great country, with resilient and creative people. And yes, no one is going to write us off, nor should they. But making the best of a bad job doesn't alter the fact that it isn't smart to put yourself in that position unless you have to.

Most extraordinary of all, the two great achievements of British diplomacy of the last decades in Europe, supported by Governments both Labour and Conservative, – namely the Single Market and European Enlargement – are now apparently the two things we most regret and want to rid ourselves of!

The Single Market has been of enormous benefit to the UK bringing billions of pounds of wealth, hundreds of thousands of jobs, and major investment opportunities; our trade with an enlarged European Union has meant for example that trade with Poland has gone from £3bn in 2004 to £13.5bn in 2016. Nations that came out of the Soviet bloc have seen themselves safely within the EU and NATO, so enhancing our own security. In addition to all this, the possibility of the break-up of the UK – narrowly avoided by the result of the Scottish referendum – is now back on the table, but this time with a context much more credible for the independence case.

We are already seeing the de-stabilising impact of negotiation over border arrangements on the Northern Ireland peace process. None of this ignores the challenges the country faces which stoked the anger fuelling Brexit: those left behind by globalisation; the aftermath of the financial crisis; stagnant incomes for some families; and for sure the pressures posed by big increases in migration which make perfectly reasonable people anxious and feeling unheard in their anxiety.

I always believe that if the centre ground does not deal with the problems, the extremes can exploit them. But our duty is to give answers, not ride the anger. Here is the paradox. As we go through this unique experiment in diplomatic and economic complexity, the entire focus of the Government is on one issue: Brexit. This is a Government for Brexit, of Brexit and dominated by Brexit. It is a mono-purpose political entity. Nothing else truly matters: not the NHS, now in its most severe crisis since its creation; not the real challenge of the modern economy, the new technological revolutions of AI and Big Data; not the upgrade of our education system to prepare people for this new world; not investment in communities left behind by globalisation; not the rising burden of serious crime; or bulging prison populations; or social care; not even, irony of ironies, a genuine policy to control immigration.

Governments’ priorities are not really defined by white papers or words; but by the intensity of focus. This Government has bandwidth only for one thing: Brexit. It is the waking thought, the daily grind, the meditation before sleep and the stuff of its dreams; or nightmares. It is obsessed with Brexit because it has to be. Future historians will be scurrying to investigate the antecedents of these migrants from Europe for whose restraint, we were willing to sacrifice so much. What will they find - that they were a terrible group of people who threatened the country’s stability? They will find that on the whole they were well behaved, worked hard, paid their taxes and were a net economic benefit. So what do we do?

The Leave campaign was a coalition, some against Europe for economic reasons; some for cultural reasons. Some were ideological in their opposition; some had done a cost/benefit analysis and concluded better out than in. We must expose the agenda of the ideologues; and persuade those interested in the cost/benefit ratio. For the latter, we must – day in day out – articulate the reality: the pain is large and the gain largely illusory. But the ideologues are the ones driving this bus. The economic future which could work outside of Europe is exactly the low tax, light regulation, offshore free market hub, with which Mrs May threatens our European neighbours, but which to the Brexit ideologues is a promise of things to come.

Indeed, this is what many in business say they're being told by Government Ministers, but of course behind the hand, because this is the exact opposite of what the mass of voters are being told when promised a fairer capitalism with a better deal for the workers. This free market vision would require major re-structuring of the British economy and its tax and welfare system.

It will not mean more money for the NHS but less; actually it probably means a wholesale rebalancing of our healthcare towards one based on private as much as public provision. It will not mean more protection for workers, but less. And if that were what we wanted to do as a country, we could do it now. Europe wouldn't stop us. But as of now the British people would, because they wouldn't vote for it. So the ideologues know they have to get Brexit first; then tell us this is the only future which works; and by that time they will be right. In defeating them, we have two major challenges.

There is an effective cartel of media on the right, which built the ramp for pro-Brexit propaganda during the campaign; is now equally savage in its efforts to say it is all going to be ‘great’ and anyone who says otherwise is a traitor or moaner; and who make it very clear to the PM that she has their adulation for exactly as long as she delivers Brexit.

It hugely skews the broadcast coverage. For example, a week ago there was the annual survey of top business bosses of the leading UK companies. Over half said Brexit was already having an adverse effect on their business. And half did not have confidence in the Government negotiating a good deal. It led the FT. It was barely covered elsewhere. The BBC had it as an item of business news. Suppose the survey had come to the opposite conclusion. It would have had at least 4 papers headlining it and would therefore have featured prominently on the broadcasts. The second challenge is the absence of an Opposition which looks capable on the polls of beating the Government. The debilitation of the Labour Party is the facilitator of Brexit. I hate to say that, but it is true. What this means is that we have to build a movement which stretches across Party lines; and devise new ways of communication. There are lots of different groups doing great work, Open Britain naturally being one. These groups must find ways of concerting strategy and tactics effectively. We should begin to create informal links immediately and then build them into a movement with weight and reach.

We need to strengthen the hand of the MPs who are with us and let those against know they have serious opposition to Brexit At Any Cost. The Institute which I am setting up will play our part. We are creating a policy platform wider than the Europe question. There is an urgent need to re-position the whole debate around globalisation and how we make it work for people. In this sense, the Brexit debate is part of something much bigger. But developing the arguments around Brexit will be an important element of the Institute’s work. We need strong links with the rest of Europe.

If our Government were conducting a negotiation which genuinely sought to advance our country’s interests, that negotiation would include the possibility of Britain staying in a reformed Europe. It is clear the sentiment which led to Brexit is not confined to the UK. There is a widespread yearning for reform across Europe. Part of our work should be to help build Europe wide alliances to give voice and effect to such an impulse.

So this movement must have many dimensions to it. It requires arguments of detail; and arguments of grandeur. The case for Europe remains rooted not in understanding the past but the future. All over the globe, countries are coming together in regional alliances for a very simple reason. As China rises, as India and other large population countries follow and with the USA already so powerful; so to maintain strength and influence, to defend our interests adequately, nations of our size will cooperate based on proximity. This is true of the nations of Europe.

But for Europe there is a more profound reason. The Transatlantic Alliance is needed more than ever; but how much stronger it is with Britain in Europe and Europe an equal partner with America. Forget the short term electoral politics there or here. In the long term, this is essentially an alliance of values: liberty, democracy, the rule of law. As the world changes and opens up across boundaries of nation and culture, which values will govern the 21st Century? Today, for the first time in my adult life, it is not clear that the resolution of this question will be benign. Britain, because of its history, alliances and character, has a unique role to play in ensuring it is. How, therefore, can it be wise for us, during this epic period of global evolution, to be focused not on how we build partnerships, but how we dissolve the one to which we are bound by ties of geography, trade, shared values and common interest?

The one incontrovertible characteristic of politics today is its propensity for revolt. The Brexiteers were the beneficiaries of this wave; now they want to freeze it to a day in June 2016. They will say the will of the people can't alter. It can. They will say Leaving is inevitable. It isn't. They will say we don't represent the people. We do, many millions of them and with determination many millions more. They will claim we're dividing the country by making the case. It is they who divide our country – generation from generation, North from South, Scotland from England, those born here from those who came to our country precisely because of what they thought it stood for and what they admired. This is not the time for retreat, indifference or despair; but the time to rise up in defence of what we believe – calmly, patiently, winning the argument by the force of argument; but without fear and with the conviction we act in the true interests of Britain.