Those inside the Westminster bubble have been transfixed, indeed bewildered, by Jeremy Corbyn’s soaring campaign for Labour leader. The more he is denounced, the better he seems to do.

Have Labour members gone mad, party luminaries wonder? Has the Militant Tendency’s 1980s entryism been somehow reincarnated from its current impotence, headlines ask? Or is the microscopic Communist party poised to determine the next leader of Her Majesty’s Opposition? Are Tories and Trotskyists paying their £3 to register votes for the same Corbyn candidature?

The two most credible candidates – Andy Burnham and Yvette Cooper – have been underwhelming: cautious and austerity-lite. You might have thought Labour had just suffered a minor setback, not an almighty election defeat whose roots lie in the loss of 5 million voters from 1997 under New Labour, 4 million of those under Tony Blair.

Labour’s grassroots are crying out for inspiration and the decent, principled Corbyn has struck a chord

Labour’s grassroots are crying out for inspiration and the decent, principled Corbyn has struck a chord. Nobody – least of all him, ironically – imagines he could be prime minister, or even that as opposition leader he could survive the high noon bearpit of Prime Minister’s Questions, or deliver an effective instant response to a George Osborne budget speech.

But at least this serial rebel under the New Labour government is defending its economic record, attacking austerity and raging at rising inequality.

Before the banking crisis, Britain had enjoyed under Labour a record 10 years of continuous economic growth; low inflation; low interest rates; record employment; big cuts in child, pensioner and working poverty; dramatic reductions in NHS waiting times; record infrastructure investment; and improved living standards.

Both the budget deficit and national debt were internationally low – significantly lower, indeed, than inherited from the Tories. In September 2007 even David Cameron and Osborne publicly pledged to match Labour’s spending plans.

Yet, barely a year later, they opportunistically switched to mounting their big deceit that “ruinous overspending” by Labour, rather than the 2008 global banking crisis, had left the country with mountainous levels of debt and a huge budget deficit.

The truth is Labour’s budget deficit then of £39bn or 2.7% of GDP was dwarfed by the colossal cost of saving Britain’s failing banks, which by 2009 was equivalent to some 90% of GDP.

At least Cooper has pointed this out, while Burnham and Liz Kendall have regrettably repeated the Tory myth that our deficit before the banking crisis was “too high”, when something lower would have been totally irrelevant to its stratospheric impact.

But the reason I won’t vote for Corbyn is that, underneath his appealing slogans and rousing values, there is no programmatic substance. Whatever their respective merits, proposals to scrap Trident, abolish tuition fees and renationalise the railways do not constitute a coherent platform.

His economic policy amounts to an unelectable platform of “tax and spend” – an anguished cry of protest, not a serious alternative for a Labour government seeking to reject the suffocating neoliberal orthodoxy of cuts, shrinking the state and privatising everything possible.

He demonstrates little understanding of the immensely arduous challenge of electing, let alone running, a social democratic or democratic socialist government, when neoliberalism is so destructively dominant globally and the British media mostly in hock to it.

For Labour, the key to bringing the public finances back into balance without further austerity is to speed up the pace of growth, after the slowest recovery from recession since 1945, with things getting worse not better: growth slowing, even more savage cuts in the next three years than between 2012 and 2015, and interest rates heading up.

As I show in my book, Back to the Future of Socialism – citing the respected Institute for Fiscal Studies, Oxford Economics and other top economists – through faster, fairer, greener growth, the public finances can be brought into balance, and the national debt and deficit reduced without further cuts.

Osborne’s Victorian, permanent budget surpluses – except during recessions – is pre-Keynesian neoliberal dogma, requiring a constant squeeze on public spending: his equivalent of the Tea Party “starve the beast” strategy in the US, which is dogmatically political, not soundly economic.

Instead what is urgently needed is sufficient public and private investment to establish the high-quality infrastructure, the millions of new houses, the high skills and cutting-edge technology to sustain a competitive productive economy. Surely this would be far better than copying the current Tory policy of building UK prosperity upon a consumerist chimera of high personal debt, artificially inflated housing assets and a disastrous trade gap?

Labour’s historic mission needs resurrecting based on hard-headed economics and evidence – a modernised Keynesianism if you like. Then the Corbyn bubble will subside and the natural majority in Britain for Labour’s values of social justice and a strong economy can be reassembled for the party to win again.

But is anybody else in Labour’s budding leadership listening?