It would be a shame to let one’s enjoyment of this spectacle – of long-term enemies Iain Duncan Smith and George Osborne exploding with animus like maturing boils – stop one lodging a concerted critique of the building consensus: that they have to attack each other because there’s no opposition. Jeremy Corbyn opposed Osborne’s budget with absolute clarity; he fixed on its main injustice – the attack on disability benefits – and established it as the culmination of six years of false narratives and dodgy maths, sleight of hand and meaningless tub-thumping. In John McDonnell and Owen Smith, he fielded allies who vowed to reverse the chancellor’s changes without caveat.

Iain Duncan Smith quit due to Treasury refusal to consider pensioner cuts Read more

While it may please the Conservative media to find Corbyn’s remarks indistinguishable from anything Ed Miliband or Balls would have said, closer or less partial observers will remember this was never quite their modus operandi. The last Labour leadership would always go in with a qualification, a “while we accept the urgency of cutting the deficit” here, or a “cuts must be made, but …” there. It always sounded more like nagging than opposing.

However, there is buoy of truth keeping the canard afloat: Corbyn’s opposition didn’t look like a traditional one because his bench, front and back, didn’t respond in the time-honoured way. During a shadow leader’s budget speech, while it’s understood that his party is behind him, they never simply take that as given. Their job is to caterwaul and holler, repeat key words and phrases, perform a vaudeville-zoo display that leaves no one in any doubt as to the sturdiness of their support. The MPs of Corbyn’s party spend his speeches checking their phones, as if they have all been replaced by their teenage offspring.

Corbynistas tend to explain this as the fault of the treacherous moderates, but I think there is more beneath the surface. The parliamentary game must be played by everyone – leader and led – in a particular frame of mind: it is characterised by an absence of doubt, and with great bolts of energy and self‑belief. Corbyn simply cannot mask his weariness that an incredibly obvious point of moral truth – the dignity of poor people should not be sacrificed to the primping of the rich – still has to be stated.

Whatever the reason that they cannot present themselves as Corbyn groupies, Labour MPs have to build a better story

He’s like a Hawkwind tribute act: it’s so plain to him that Silver Machine is the best song on Earth that he doesn’t put enough welly into the chords. His backbenchers could yelp and cheer, but they run the risk that he will turn round with a teacherly eyebrow that asks them what, precisely, all that noise is about. This account is more plausible than its alternative, that they prefer Osborne’s programme to their own leader’s. Whatever this party’s fissures and vanities, they are still social democrats. They did not come into politics to throw disabled people under a bus as proof of their commitment to the lean and competitive state.

Whatever the reason that they cannot quite present themselves as Corbyn groupies, Labour MPs have to build a better story rather than simply remaining silent. It is theirs for the taking: there is a 21st-century response to this, which clicks into a broader narrative.

Facebook Twitter Pinterest Iain Duncan Smith leaving BBC New Broadcasting House after appearing on the Andrew Marr show on March 20. Photograph: Chris Ratcliffe/Getty Images

First, the labour market that the Department for Work and Pensions describes bears no relation to reality. The “non-binary world” that “compassionate” Conservatives yearn for in which disabled people can move between categories of “fit” and “unfit” with their fluctuating health, relies on a jobs market that is casual but still caring, where positions are held open, support is a given, fairness and empathy flow freely.

What we have instead is a market in which flexibility is all in the employer’s favour, zero-hours contracts undermine the stability of workers regardless of their health, and minimum wage legislation is routinely undermined by the extra time it takes to strip-search your staff as they leave. It’s an atmosphere of hyper-surveillance and radical mistrust. There is room in this debate for a forward-facing MP to ask not are disabled people working hard enough for employers, but are employers working hard enough for disabled people – or, for that matter, anybody else.

Second, it is time to unpick the goal of social mobility, which is just a benign phrase for “survival of the fittest”. We need to concentrate not on a society where the ambitious can prosper, but build one in which the least economically productive still live in comfort and dignity. None of us is productive all the time, some of us aren’t productive any of the time – but we’re still as human as one another. This is an opportunity to make the point that freedom, for so long framed as the ability to compete and consume, is meaningless if your basic needs aren’t met. To chip away at any group’s means of sustenance is to be a government actively working against personal freedom.

Third, the intricate variety of disability is blurred on the left, while it is forensically examined on the right in order to erode benefits in a systematic way. Those who are cognitively able but physically impaired saw their lives bludgeoned with the closure of the independent living fund.

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It left people who were previously in fulfilling careers stuck at home, sitting on an incontinence pad, waiting for two 15-minute care worker visits to top and tail the day. People with a learning disability saw their main employer and support structure, Remploy, privatised, its factories shut down, its other functions contracted out to Maximus, the same American company whose other government work is to inform people that they never had a disability in the first place.

Those who are too disabled to undertake work of any kind have been hit in other ways: a change of indexation rules, the bedroom tax, cuts in housing benefit, cuts in adult social care, higher eligibility criteria and so on. All these people have been rigorously, though tacitly, differentiated by a government determined to give no quarter. In order to universalise the case for dignity, the left needs to humanise this debate.

The opposition, far from being silent, is articulate, reactive and energetic – but by its nature it is insufficient because this territory is so vast, touching on everything we understand by freedom, citizenship, work, dignity and society. Even the brief allegiance of disaffected Tories isn’t enough. What is needed is a symphonic response from those who believe that politics isn’t about protecting people from the future, but building a future that is better.