David Cameron’s pitch in the Guardian that “red warning lights are flashing on the dashboard of the global economy” will no doubt draw some wry smiles from readers, with good reason.

Ah, so when global tremors threaten a Conservative government, it’s not their fault. But when the greatest global crash in generations strikes a Labour government, the cause is Gordon Brown overspending on tax credits for the low paid. Looking for foreigners to blame is no surprise, since as things stand under Cameron and George Osborne, debt is rising; the deficit is on the up again; welfare spending is £16.5bn overshot due to high rents and low pay; Treasury receipts are falling; living standards are flat or down after three years of flat-lining austerity; while inequality rises and social mobility sinks.

With a risky hubris, Cameron and Osborne trumpet a growth rate over most in the G20. Yet something tells them this may not stand up to election scrutiny. Office for Budget Responsibility forecasts in December’s autumn statement may be less rosy. The Institute for Fiscal Studies warnings of Osborne’s impossible £48bn of cuts to come are unnerving. Besides, whose growth is this?

So they cast about to lay the blame on a dangerous outside world of Ebola, Syria, Ukraine and, above all, failures in the feckless eurozone. The economy was to be their golden ticket. Keep off Europe and immigration, say advisers, that’s Ukip turf, as we shall see in Rochester and Strood this week. Get back to the bread-and-butter, stupid. But what if people don’t see any butter on their Osborne bread? Few believe Cameron’s promised tax cuts. Boasting that the economy is out of trouble risks leaving voters free to opt for less austerity next time, so here’s the corrective: hold on to Nurse Cameron for fear of something worse.

It’s for Labour to offer something better. And it can. By cutting the deficit more slowly, it has at least an extra £30bn to ease the coming pain, calculates the Resolution Foundation. It leaves open the door to borrowing for infrastructure investment for a million homes, transport and good jobs.

But last week Ed Miliband bet the bank – plus bankers’ bonuses – that ballooning inequality was the great issue of our time. He’s not alone, as the International Monetary Fund, the World Economic Forum and even Mark Carney of the Bank of England identify it as the root cause of long-term economic woe: if too many are paid too little, who buys the goods and pays the taxes?

In his “zero-zero economy” speech Miliband threw off inhibition to hammer out his long-term theme – how inequality, insecurity and low pay cause a standard of living crisis that looks dangerously like the new normal. This is Labour’s authentic message, not political calculation or a left lurch, but what the party’s for. The pretence that Labour is anything else always reeked of the Westminster dissembling and inauthenticity that drives voters away. For both main parties, the middle ground begins to look more like a death zone than the winning turf.

“Ah, a 35% core-vote strategy,” sneer some commentators, warning that Labour risks alienating business and the well-off. But businesses rarely back Labour, the Confederation of British Industry tolerating it only when Labour victory is imminent. Miliband’s CBI speech laid it out to them: if business leaders genuinely protect their companies’ interests, they put keeping Britain in Europe before their personal tax interests. As for the well-off, Labour attracts a fair slice of highly educated well-paid group ABs; most of the rich are beyond reach. Beckoning “core” voters is authentic Miliband, as well as good strategy, to bring back all who ever voted Labour and the non-voting young.

Parties seek a sharper definition and a clearer purpose: voters rightly demand a reason to rule beyond Cameron’s laconic “because I thought I’d be good at it”. As the Tories blur indistinguishably into Ukip, Miliband is right to focus on the rising tide of inequality, a hotly contested ground.

Take the front pages of two opposing newspapers last Sunday. The Observer led with “Revealed: how coalition has helped rich by hitting poor”. Research from the LSE’s John Hills and Essex University finds tax and benefit changes since 2010 cause the poorest to bear even more of the brunt of austerity than official figures show. A few of the top 5% took a small hit, though astonishingly, the top 1% have been net gainers. The lowest paid in the bottom 10% took a 5% hit. Families with children and lone parents lost most, with cuts exceeding any tax allowance gains. Previous figures were fiddled by the Treasury by pretending Labour’s tax rises on the rich happened under the Tories. This confirms all Miliband said. As Ed Balls adds: “It demolishes any last pretence that we are somehow all in this together.”

Now turn to the Telegraph: “How top 3,000 earners pay more tax than bottom 9m.” Those earning over £2.7m contribute 4.2% of all income tax, while the lowest-paid third contribute 4%. Its editorial says: “It is the height of foolishness to drive wealth creators away through threats of raising the highest rates of income tax or a ‘mansion tax’.” “Soaking the rich” is no answer, nor is “taxing, spending and regulating our way to fairness”. Nowhere does it say that people would pay taxes more equally if there was fairer pay.

Both sets of numbers are true and what you think of them determines how you vote. Telegraph figures conveniently only relate to income tax, where the lowest third pay little because they earn little but pay more of their income in VAT. If the Treasury’s dependence on mega-earners is sacrosanct then the rich can only go on getting richer. Miliband’s “zero-zero” was a rhetorical flourish, calling for better pay and clawing back the £34bn (some say much more) from the evaders and avoiders and the Luxembourg shirkers, from Dyson to Amazon.

Shocking facts keep charting Britain’s rising social divide. Do statistics percolate through to most voters? You have to believe that in the end they do, drip by drip, despite the welter of the right’s misleading anecdotes that try to show the Benefits Street poor are the cause of their own condition.

People feel in their pockets what the LSE/Essex University figures show, that the middle and lower half are deliberately made to pay the price, while Osborne gifts the richest the most. No wonder Cameron hopes he can blame any feelgood shortfall on the state of the world beyond.