If anyone could actually enjoy the slow-motion car crash that the Labour Party is going through, you might think it would be me. After all, during the five years of the Coalition government, Labour’s favourite pastime was calling me a traitor, a quisling, a sell-out and every other damning name under the sun. They yelled in the House of Commons, protested outside my home and my office, posted unprintable stuff on social media and erected a huge poster in the centre of Sheffield depicting me as “Cleggzilla”.

It was the sort of no-holds-barred vilification many moderate, centrist Labour MPs now complain they are receiving from the hard Left of their own party. Oh, diddums. Poor, sensitive souls. I have to admit, it is sometimes tempting to stand back and enjoy watching Labour getting a taste of its own medicine. Except I can’t. Because Labour’s crisis is not comic. It is tragic and it is bad for our country.

Over the past year or so we have all seen what happens when a single-party government is allowed to rule with no effective Opposition at all. The Conservatives have indulged all their prejudices — budgets targeting the working poor, a knife held to the BBC’s neck, petty fights with junior doctors — with none of the checks and balances a viable Opposition should provide.

Not only was the referendum thrust upon the country simply to settle an internal Tory feud, but now that it is over we have the sordid spectacle of Tory contenders stabbing each other in the back as they vie for the crown. The Conservatives have brought our economy to the brink of another deep recession and are presiding over the most dysfunctional government in living memory — yet they and their supporters in the press carry on as if they are born to rule. If there was any justice in the world, they would be disqualified from governing our country again. Never in modern times has a political party gorged itself on its own obsessions with such devastating consequences for the rest of the country.

And where is the main party of opposition? Fighting among themselves. The Lib Dems, the SNP and the Greens can do their bit to hold the Government to account in Parliament, but it’s Labour’s job as the principal party of opposition to oppose.

It’s not my place to pick sides in any leadership contest, but for the good of our country I sincerely hope Angela Eagle, Owen Smith or someone else can break the impasse.

Jeremy Corbyn is clearly a man out of time — in more ways than one. He seems polite and sincere, and the support he has inspired from thousands of young idealists is genuine and exciting, but for all his talk of a new way of doing politics, the politics he wants to pursue is trapped in the culture wars of the 1970s.

Take, for example, the referendum campaign. Jeremy Corbyn’s ambivalence was there for all to see, even in the face of the pro-European enthusiasm from many of the young Labour activists he has inspired. In the end, it was in part lost because of Labour’s inability to reach out to communities it had previously considered its own.

If you look at the map of the results, some of the biggest Leave wins were in places Labour has considered its strongholds for decades — especially in the North-East, the North-West, Wales and Yorkshire. I saw it for myself in Sheffield, which voted narrowly to Leave, where the biggest margins for the Leave campaign came in the urban seats that have returned Labour MPs for decades.

Brexit is a momentous constitutional issue with profound ramifications for the whole United Kingdom. As we figure out what our new relationship with our European neighbours is to be, there is a fundamental dilemma that needs to be resolved: if we want to retain access to the single market in a Norway-style arrangement, we’ll have to accept a significant loss of control over the rules governing our economy; if, however, the Conservatives insist on pulling us out of the single market we’ll have to accept years of lower growth and higher unemployment. There is no way round the invidious position we now find ourselves in. What is better for our economy is worse for Brexit politicians who promised to “take back control”, and what is better for those Brexit politicians is worse for our economy.

These arguments need to be thrashed out openly and democratically. It can’t just be left to the Conservative leadership contenders and their cheerleaders in the Right-wing press to decide our fate. We need a Labour leader who cares about this. We need a Labour Party that is capable of setting out an alternative vision for how Britain can maintain its open, outward-looking economy. Jeremy Corbyn patently has no interest in leading this debate. It’s not his cause, not his fight.

Most importantly, Labour needs a leader who gets that the world around them is changing and changing fast. If there’s one thing the referendum has shown it is that the fault lines of opinion in our country are no longer reflected in our political parties in Westminster.

We need leaders, like Tim Farron of the Liberal Democrats, who recognise that politics is becoming increasingly fluid. The Left-Right debates of the 20th century — market versus state, private versus public, low tax versus high tax — are being usurped by arguments between openness and isolation; internationalism and nationalism; social conservatism and social liberalism.

As those of us on the progressive side of politics try to find our voice in this new context, the last thing we need is senseless tribalism. We need grown -up politics in which leaders talk to each other and even, heaven forbid, work together. That’s why the Labour Party needs grown-up, pragmatic leadership, not just for its own sake but for the country’s too.