All this week, the Liberal Democrats have gathered knowing they have no chance whatever of winning the next general election. Next week, the Labour Party will do the same. That is the sad reality of what has happened to a party that just a decade ago looked like it had finally reversed the Tory dominance of UK politics, a reality underlined by the inevitable re-election of Jeremy Corbyn as leader.

In 1935, a man named George Dangerfield wrote a book entitled The Strange Death of Liberal England. I have the horrible feeling that we may be living through the death throes of Labour Britain, and possibly even the Labour Party itself. Here is a deeply untrivial trivia question for you. How many Labour leaders have won a General Election in the last forty years? (For the answer, keep reading.)

Parties do not have a divine right to exist, let alone to thrive. Look at Scotland, where not long ago working class support could be taken for granted by Labour – and alas, in many ways, was taken for granted – until an alternative came along in the form of the SNP that suddenly seemed more relevant to people's lives.

So this decline began before Corbyn emerged as successor to Ed Miliband. He cannot be blamed for the rise of the SNP, nor for David Cameron's unexpected majority. But he, his politics and his inability to lead can be blamed for the catastrophic position we are in now, where we have rarely appeared less relevant to the majority in this country who do not live their lives obsessing about internal party political machinations.

Corbyn's Labour seems to inspire three very different feelings. Inside the party, a near religious fanaticism among those he has inspired to join, and a more sinister and pragmatic version of that fervour among the old hard left exploiting his leadership to gain more power in the party. The second feeling is something closer to despair among those who share my obsession that to make real change in politics, you must win power in parliament. And thirdly, there are the non-bubble-living, non-political-obsessives who dip in and out of the debate, get on with their lives and every few years decide how to vote. The thing I most commonly hear from them right now is that 'you lot have had it.'

'Of course we can win,' the party's leaders will say whenever a microphone is thrust before them at the conference in Liverpool. The pro-Corbyn people will say all that needs to happen is 'unity behind Jeremy'; the anti-Corbyn people will say that what needs to happen is that Jeremy goes, and then rebuilding can begin. But both know the next election is all but lost, and there are many in the first group who seem deeply untroubled by that.

There have always been activists for whom power in the party is more important than power in the country. The big difference now is that they are the people in charge.

They talk a lot about honest, straight-forward politics, and of Corbyn's rise being a rejection of New Labour 'spin.' That would be the spin that shadow chancellor John McDonnell – as you may have seen on BBC Question Time last week – prefers to define as the Blair legacy ahead of a minimum wage, Sure Start, the New Deal, gay rights, the biggest schools and hospital building programme in our history, debt relief in Africa, the Good Friday Agreement... I could go on for a few pages, but you get the point.

In their honest, straightforward politics, Corbyn's Labour was ahead in the polls until Hilary Benn resigned from the shadow Cabinet and triggered a so-called 'coup'. They were not. Of 89 polls, the Tories had been ahead in 85, Labour were neck and neck in four. In their honest, straightforward politics, council and by-election results were a great success. They were far from it. In their honest, straightforward politics, only a 'small minority' of MPs felt Corbyn and his team were incapable of providing the leadership the party needs.

Owen Jeremy
The two Labour Leadership Candidates, incumbent Leader Jeremy Corbyn and the challenger Owen Smith MPGetty Images

On the contrary, as the nominations for Owen Smith showed, it was an overwhelming majority of MPs. In their honest, straightforward politics, Corbyn fought hard for Remain in the referendum (yet many of our own supporters thought our official position was Leave, and his lack of interest in Brexit since has been an abdication of any sense of national leadership).

Now in their honest, straightforward politics, they are talking about 'reaching out' to unite. They have a very strange way of showing it. Talking the talk about condemning abuse and stirring up hatred against sitting MPs, while mobilising the forces to do it. Siding not with the victim of anti-Semitic abuse, Ruth Smeeth, but her abusers. Targeting the one southern MP, Peter Kyle, who took a seat off the Tories at the last election for deselection. Setting up the party's elected deputy leader Tom Watson to fail when he brings forward plans to heal the rifts in the PLP. Undermining party staff and especially the general secretary Iain McNichol for daring to run the leadership election according to party rules rather than as a fan club for Corbyn.

The posh boy revolutionaries who are pulling the strings in all this really don't care. The more inward looking we become, the more it suits their game.

Last night's news took us way back to the Party's darkest days. Some massive issues going on, home and abroad, world leaders gathered at the UN, the Syrian ceasefire collapsing amid what might be a Russia-Syrian war crime, a heartrending report on starvation in Yemen, the Brexit fallout/fiasco continuing, more bad news on the NHS and social care, a rise in gambling addiction among the young... and meanwhile Labour took eight hours to fail to agree how the shadow Cabinet should be chosen.

What did the Syria story and the Labour story have in common? They both involved 'peace talks'. When a political party that is supposed to be a gathering of like-minded people with shared goals and objectives has to have 'peace talks' a few days before its annual conference, you know it is in big trouble. Worse, the posh-boy revolutionaries who are pulling the strings in all this really don't care. The more inward looking we become, the more it suits their game.

As to my quiz question, the answer is one. Tony Blair. One Labour leader in four decades has won a general election. I say that not to fly the New Labour flag, but to emphasise how hard it is for progressive left of centre parties to win power in this country. We are about to make it a whole lot harder, with disastrous consequences for Labour, and for Britain.

In a couple of weeks, I am publishing the fifth volume of my diaries, which run from the day I left Downing Street in 2003 to the day Tony Blair won his third election in 2005. I know we live in uncertain times, but the way things feel right now, it could be an account of our last ever election win. I hope not. But it certainly feels like it.