When the exit poll appeared on our screens at 10pm on 7 May, the floor gave way beneath the Labour Party. Like me, every candidate, activist and supporter across the country felt a sickening sense of disappointment and disbelief. It got worse than we all feared at that moment. We got a majority Conservative government.

Since that fateful night Jeremy Corbyn’s meteoric rise to the leadership has had a profound and far-reaching impact on the Labour Party, and on the political landscape more broadly. Throughout his impressive and highly effective leadership campaign Jeremy made it clear that he wants a truly open, inclusive and constructive conversation about the future of the Labour Party: how can we craft an inspiring new vision and narrative? What should our new policy priorities be? How can the Labour Party regain the trust of the British people, become an effective opposition, and ultimately return to government in 2020?

In order to be able to answer any of those questions, we must first of all understand where it all went so wrong. For me, the fundamental weakness in our last 5 years was that we talked a lot about what we were against, but said little about what we were actually for. We rightly expressed our outrage about growing inequality and injustice, but did not speak enough to people’s hopes or ambitions. The electorate didn’t understand our vision for society, because we didn’t really tell them what it was. They heard us repeatedly hammering the bedroom tax and zero-hours contracts, and their response was: “I agree with much of that, but what does it mean for me when I’m not on zero hours, or liable for bedroom tax? How would a Labour government help me and my family to do better?”.

On 7 May, the message from the majority of the British electorate was clear: we think that you don’t really care about us, the hard-working families who are trying to get on in life. That feeling was wrong, but it was strong. Labour was rejected because we seemed to be focused exclusively on a narrow, disadvantaged section of the population, when it’s blindingly obvious that political parties only succeed when they have broad appeal.

In my recently published pamphlet – A New Nation: Building a United Kingdom of Purpose, Patriotism and Resilience – I argue that if Labour is to have a chance of winning in 2020 then we must do three things:

First, we have to convince the British people that we can once again be trusted with the economy. We have to make it crystal clear that our top priority in government will be to balance the books by modernising the welfare state, and by delivering purposeful policies that foster investment, competitiveness and sustained growth. Re-building our relationship with large and small businesses, heeding their good ideas, must be a vital part of this new approach.

Second, we have to reclaim patriotism. I’m proud to be British and I love the UK as a united country of fair play and liberty, bound together by our shared values of compassion and of courage. Decentralising power and resources, putting the English regions on a similar footing to Scotland and Wales, making governments listen, celebrating what is best about Britain: these are the qualities that should drive our new patriotism. And this renewed sense of localism and civic pride will provide us to stand tall in the world, inspired by the confident patriotism that flows upwards, from cohesive communities. In this age of insecurity it’s more important than ever that we engage constructively with Europe and NATO, so that we can have real influence on the decisions that impact directly on our national interests and security.

Third, we have to show that Labour is the only party that can deliver the radical changes that are necessary if we are to build a more resilient country. In a world that’s in a constant state of flux the successful countries will be those that are quickest to recover from unexpected events and adapt to new realities. High skills, properly funded research, an economy that is not dependent on huge household debt, and a manufacturing renaissance: these must be cornerstones of our new resilience.

By the time we got to 7 May most voters had come to the conclusion that when we were speaking about fairness we meant dragging people who have done well down, rather than the idea that investing in society is actually about building a springboard for everyone to chase their dreams and realise their full potential, if they are prepared to work hard for it. “Labour,” said one of the founding fathers a hundred years ago, ‘is for the elevation of all classes, not the destruction of any.’

But what that means now has changed beyond recognition since the day that I joined the Labour Party in 1985. People simplistically say that, in order to win, Labour has to ‘reconnect with its working-class roots’, and that it is possible for us to gain votes by ‘moving to the left’. But a cursory glance at some basic statistics tells us such superficiality is nonsense. It is true that 45 years ago, manual workers and their families (the normal definition of working class) dominated our vote, accounting for 10 million Labour voters back in the early 1970s, compared with just two million middle-class Labour voters at that time.

In 2015, the composition of the British electorate, and of our vote, is completely different. In the early 1970s two thirds of all voters lived in working-class households, but in Britain today the number of middle-class voters exceeds the number of working-class voters by seven million. In addition to being substantially smaller in size than it was 40 years ago, the working class has been fragmented by de-industrialisation and the technology revolution, and so it is no longer possible to talk about it as some sort of monolithic bloc that can be mobilised around a given political cause. Indeed, it is patronising as well as illusory to do so.

It is therefore vitally important that we wake up to this new reality: we will never win another election if we attempt to present ourselves as a party that represents a narrowly defined social group. It is, quite simply, mathematically impossible.

That reality compels us to aim higher and wider. We must show that we are determined to achieve true security and real opportunity for everyone in our country. After all, everybody wants much the same: to be safe and protected; to feel they belong and have a place here; to have dignity and confidence; to be able to enjoy life; and to have a fair chance of receiving decent rewards in return for talent and hard work.

Those desires are the basis of productive self-interest, not selfishness. They represent the ambition to do better for yourself, your family, your community. We must never forget that ‘getting on in life’ is a force for good, not an excuse for envy.

7 May taught the Labour Party that niche politics is fine if we want to be a protest movement, but a dead end if we are to earn victory. Our desire for electoral victory is anchored in the knowledge that we can only put our values and principles into practice if we are in government, and we will only return to government on the basis of an inspiring new narrative that has broad appeal across the full spectrum of the British electorate.

A twenty-first century Labour Party that is truly “for the many, not the few” must therefore be sound on the economy, strong on reform, and resolute on our place in the world.

There must be no going back to the wilderness years of the 1980s. Now is the time to renew, not to retreat.