When a man is suffering from terminal cancer, he is liable to be persuaded that his best chance is to switch to a diet of broccoli juice, as recommended by his wife, who once saw something amazing about it on the internet. Friends shake their heads privately but decide to humour him. Why not, if it raises his hopes, if only for a few months?

The Labour Party is now in a very similar position. It is determinedly unwilling to believe that its electoral sickness is terminal and thinks that if only Alan Johnson – the broccoli of politics, easy to digest and delightfully flavourless – were somehow painlessly to take control, then a return to normal health could be achieved.

Perhaps we should also try to indulge the Labour Party in its delusion – but it is so much less easy to sympathise with its predicament. One of the reasons for that was summed up by the very first line of Graham Allen's article "Brown Must Go" in this newspaper yesterday. The Labour MP for Nottingham North began: "There is only one reason to have an election for Labour Party leader: to increase our chances of winning the next election." You see, it's not about providing better governance for the country as a whole. It's only about Labour MPs attempting to keep their jobs, whether as ministers or even back-benchers.

They have nothing more than this to say, however, because none of them have anything remotely resembling an alternative programme – even as they bleat continually on the airwaves about how they need a "new vision", like peasants praying at some medieval Catholic shrine. None of them have anything critical to say about a single one of Gordon Brown's policies to deal with the economic crisis. There was a time when the left of the party might have coalesced around a platform of increasing taxes on the high-paid, but Brown has already given them that, with the new 50 per cent top rate.

Even the left knows that the money has run out: under the allegedly superb economic leadership of Comrade Brown, the British Government is now borrowing more and more billions solely in order to pay the interest on our existing vast debt. Our Budget deficit is set to reach twice the level, as a proportion of national income, as it did when the Labour government of the late 1970s was forced to seek emergency financing from the International Monetary Fund.

This explains the otherwise mysterious way in which Lord Mandelson draws up economic plans which seem to have no application: his "offer" of investment in troubled Jaguar Landrover was cunningly attached to conditions which the company's owners could never accept. Meanwhile his plan to "kickstart" a British electric car industry was based on giving discounts on vehicles which do not yet exist, and may never exist. The point is that such "plans" are therefore cost-free, the only industrial strategy that the Exchequer can afford.

Gordon Brown calls these the "investments" that Labour offers, in distinction to "Conservative cuts". His strategy – and at least, unlike his internal critics, he has one – is to delay the cuts which any government would need to make, until after the general election, and present himself as the man who saved the economy. The idea that the voting public will not be able to see through this ruse is a level of self-delusion akin to Brown's earlier belief that he had conquered the entire economic cycle.

No wonder Alan Johnson is unwilling to make a grab for the Prime Minister's job, at a time when the tough choices that inevitably confront the holder of that office are now only between different ways of saying "no". This is a man who loathes any form of confrontation, and who seems, indeed, not to have an enemy in the world. That is often the sign of a very attractive personality, but it is absolutely not the hallmark of a leader – and Alan Johnson is clearly a self-aware individual.

John Major had much the same sort of reputation when he arrived in 10 Downing Street, after Margaret Thatcher was despatched by a rebellious Cabinet and Parliamentary Party. Nobody disliked "good old John" – and like Alan Johnson he had what is now called "a very good back story"; that is, he had overcome a childhood of economic hardship and risen to political heights without the benefit of a university degree.

The Tories under Major, it is true, managed to win the 1992 general election, against all the odds; and it is this thought which excites many Labour MPs when they contemplate doing to Brown what the Conservatives did to Thatcher. Unfortunately for them, however, there are some very significant differences.

First of all, David Cameron is not Neil Kinnock – I somehow can't see the Tory leader repeatedly screaming "weeere aaaaaaallllriiiiiight!!!!" at a premature victory rally a few days before the next general election. Secondly, Labour's current level of unpopularity is at a level which goes far beyond "the problem with Gordon". After all, Blair would never have been forced out if the party was not already suffering from dismal levels of public support. Now, however, it has sunk to positively subterranean levels: in the European elections Labour came fifth in the South East of England, and sixth in Cornwall (trailing Mebyon Kernow, the Cornish nationalists). We have heard both loyalists and rebels talk of the recent results as primarily a reflection of the public's fury at the Westminster allowances scandal, but if that were the case, one could have expected the Tories to have suffered equally – especially as their expenses claims were the more vivid – but they haven't.

Yesterday, the former Justice secretary Lord Falconer (Tony Blair's old chum, and therefore no friend of the Prime Minister) declared that his party leader should be ousted, and that "but for our weakness, the Tories would be vulnerable". Yes, and but for the absence of balls, my daughter's spaniel would be able to sire a litter.

Charlie Falconer's main argument is that "in the current situation it is so difficult for Gordon Brown, after 12 years as Prime Minister or Chancellor, to be a convincing agent of change". Here we get to the heart of it. It is true that the great bulk of the British public wants a change at the top – but little suggests that by this they mean a new leader of the Labour Party; only one opinion poll has indicated that with Alan Johnson, or David Miliband, or (fill in gap) as leader of the party, its electoral chances would be improved.

No, what most Britons want is a general election. That, in our democratic system, is how political "change" is achieved, not by one party engineering a series of private putsches against whichever leader of the time is deemed to have outlived his election-winning capability.

If the Labour Party were truly interested in national '"political renewal", it would at least consider taking up the challenge of democracy. Instead the Cabinet appears to believe that the best argument for retaining Gordon Brown is that if Labour switched to yet another prime minister without consulting the public, the calls for a general election would be irresistible. So it will probably stagger on to the bitter end of its thoroughly depleted mandate, dying a little bit more each day.

d.lawson@independent.co.uk