It’s a measure of the triumph of the pro-austerity argument in Britain that George Osborne presented his latest round of cuts in the Commons last week – a down payment on the £25bn he plans to make over the next three years – as a “culture of good housekeeping” in government. Austerity as common sense.

With a historic general election victory under their belts, and Labour still obsessed with repudiating their own general election manifesto – and even trashing spending decisions Gordon Brown made seven or eight years ago – the Tories have a wide open field. But the forthcoming onslaught on the public services cannot be left unopposed.

First, the spending squeeze the Tories now hope to implement, starting in the current financial year, is intense, as the spreadsheet wizards at the Institute for Fiscal Studies made clear last week. Shortly before Osborne’s statement, Carl Emmerson, the IFS’s deputy director, warned that achieving the Tories’ planned cuts would be “anything but easy”.

Rising cost pressures, not least an ageing society, and protections for cherished areas, including the NHS and overseas aid, mean the pain for other departments will be severe. By 2015, if Osborne proceeds as planned, the budgets of “unprotected” departments, including the Home Office and Department for Business, will be more than 30% lower in real terms than when the 2010 coalition came to power.

As the Institute for Government’s Julian McCrae spelled out at the same seminar, there are already warning signs that parts of the public services are creaking. He cited a sharp increase in waiting times at hospital accident and emergency departments, and rising violent assaults in prisons as staff numbers are cut, as examples.

So far, surveys suggest the public are only reporting modest deteriorations in services as a result of the past five years’ savings. But as the attrition continues, opinion is likely to shift. Certainly Nicola Sturgeon was able to win a significant hearing for her anti-austerity stance during the election campaign, albeit that the details of the SNP’s spending plans didn’t quite support her fiery rhetoric.

Less than 25% of UK debts is owed to overseas investors and there is little evidence that bondholders want fresh cuts

Second, the belt-tightening is likely to be profoundly unfair. Osborne has repeatedly said his cuts plan will involve a £12bn reduction in the welfare bill. Since pensioners are protected, and out-of-work benefits are a relatively small part of the £250bn social security budget, much of the burden is likely to fall on low-wage workers and their children – through reductions in tax credits or housing benefit, for example.

This comes as his party is pledged to cut inheritance tax for property owners (kids whose parents’ home is worth less than £650,000 already don’t pay it) and raise the threshold for paying the higher rate of income tax – two reforms aimed at middle and top earners.

Third, more austerity is risky at a time when recovery appears to be fragile against a background of the bubbling eurozone crisis.

The argument that sucking demand out of the economy through public spending cuts could jeopardise growth may have been trounced in pre-election debates – but that doesn’t mean it isn’t right. Amartya Sen, the Nobel-prizewinning economist, wrote an elegant essay in the New Statesman last week damning what he called “the confused anxiety, not to mention the orchestrated fear, that seems to run down the spine of the terrorised British today, making austerity look like a fitting response”.

He argues forcefully that a nation’s debts are mainly owed to someone else within the same society – for example the pension-holders whose funds are stacked full of gilts.

Less than a quarter of the UK’s debts are owed to overseas investors and there is little evidence to suggest bondholders want fresh cuts. As Jonathan Portes of the National Institute for Economic and Social Research pointed out last week, there was almost no visible reaction in the gilt market to the Tories’ surprise election victory, which implied a considerably tighter future fiscal policy than most of the polls were predicting.

Separately, a report from the International Monetary Fund, rarely considered a hotbed of fiscal recklessness, warned about the risks of trying to tackle a country’s debt burden too quickly. It’s not that the IMF believes hefty debts don’t have bad consequences for economies – but for countries in what it calls the “green zone” (in which it includes the UK), which can borrow cheaply with little danger of being shut out of capital markets, it suggests the best option might be to live with their debts. Paying them down rapidly distorts the economy too much to be worth the risk.

Debts should be “reduced organically through growth, or opportunistically when less distortionary sources of revenue are available”, the IMF’s researchers argue. Meanwhile, the Organisation for Economic Co-operation and Development, previously a cheerleader for Osborne’s cuts, has urged him to smooth the path of public spending to make it less economically damaging.

So the cuts are larger than Osborne and his colleagues let on; they may threaten the quality of cherished public services, place an unfair burden on those who can least bear it, exacerbating inequality – and jeopardise the very economic growth which is ultimately the best way of tackling the deficit.

Labour’s proto-leaders are right to try to learn the lessons of the campaign and seize back the language of “aspiration”. But they must not abandon the central insight that austerity is not a necessity, but a political choice.