They cheered, they guffawed, they mocked. Picture the scene, and don't forget it as the next two and a half years of Cameron's Britain drag on: a smug pack of over-paid Tory MPs – some worth millions – sniggering as they prepared to slash the incomes of Britain's already struggling poor. Labour's Lisa Nandy and Ian Mearns pleaded with them in the Chamber, vainly, to stop laughing. Not since 1931 has a Government attempted to deliberately, consciously reduce the incomes of the poor. Oh, the hilarity.

The cap on in-work and out-of-work benefits is the culmination of a systematic campaign by the Tories and their media allies to turn large sections of the population against each other. “Strivers” versus “skivers” and “shirkers”; sinister images of the workshy and feckless with their curtains drawn: this is a near-daily diet of poison in Cameron's Britain. The substance of their argument is this: you have been mugged and therefore your less deserving neighbour should be mugged too. They said it to private sector workers about their counterparts in the public sector, attempting to stir up envy at their supposedly over-generous “gold plated” pensions and pay settlements. Now the Tories attempt to exploit the resentment of public sector workers languishing under a de facto pay cut they have imposed themselves. Where is the justice if we do not pick-pocket your neighbour, too, with this benefits cap? There is a Yiddish expression - “chutzpah” - for such unapologetic shamelessness.

A government of millionaires makes the poor poorer while trying to turn them against each other. And so a new generation learns to appreciate the passion behind Labour pin-up Nye Bevan's famed declaration in 1948 that the Tories are “lower than vermin”.

They jeer and they whoop now, but this is surely overreach. “Today Labour Are Voting To Increase Benefits By More Than Workers' Wages” is the latest Tory hit poster, claiming that they are “Standing Up For Hardworking People.” The Tories' recently hired arch-spinner Lynton Crosby has been quick to inject his own brand of bile into the Tory operation. But this divide-and-rule propaganda makes no sense. Both those who work for their poverty and those who are without a job are having their pockets emptied by a cabal of ideologically-crazed millionaires. It is quite true that both private and public sector workers have faced years of flatlining or declining wages. But now millions of them will be hit with reduced tax credits, too. They must not get away with playing off people receiving benefits and workers facing shrinking pay packets: they are one and the same. First you are mugged by your boss, then you are mugged by the Tories.

The baying of the Tories is loud enough; the voices of those affected have been all but airbrushed out of existence by the political establishment and a supine or sometimes criminally complicit media. Save The Children recently revealed a world that most of the commentariat don't even know – or want to know - exists: of parents choosing between heating their homes and feeding their kids; or skipping their meals to make sure their sons and daughters are nourished. Such is the conspiracy to deprive the electorate of the truth about the Government's onslaught on the welfare state that many don't even know they are about to be hit. With the Resolution Foundation projecting a 15 per cent decline in income for low earning families by 2020, they'll know soon enough. Research by the TUC last week showed that the more people know about the realities of the welfare state – about fraud, who gets benefits and how much they are really worth – the less likely they are to support Tory attacks. Here is the potential undoing of this vicious campaign.

And what of the Lib Dems? Granted, it is a question that answers itself. Four votes against and two abstentions excepted, every last yellow-bellied man and woman marched through the voting lobbies with their Tory masters to shrink the incomes of the poor. That includes Tim Farron, the posturing Lib Dem President who will undoubtedly one day attempt to claim the leadership of whatever remains of this disreputable, discredited party: he may well be able to drive his diminished parliamentary party around in a London cab after 2015, just like the good old days of British Liberalism. “Many of us have been fighting the corner of vulnerable people for months and months now,” he tweeted me before voting to slash their income, “And I'll keep doing that every single day.” I'd suggest he was Machiavellian, if I was not in danger of inventing strategic ability where there is none. More than any other Coalition policy, this scandalous, grubby episode has exposed a rootless party, devoid of principle, stuffed with vacuous non-entities and mealy-mouthed voting fodder for the worst attacks inflicted on the poor since World War II. No forgiving, no forgetting; the dustbin of history awaits them, and deservedly so.

This is not to let the Labour leadership off the hook. They were right to take on this cap – though, quite frankly, what is Labour for if it is not to defend the working poor and unemployed from Tory muggers? Yet it was a decision taken in the face of internal opposition behind the scenes from the party's Surrender Tendency. Former Home Secretary Jacqui Smith came out and openly savaged Ed Miliband for it. A period of silence would be most welcome, Jacqui.

But Labour's response will always be hobbled when it is delivered by the likes of Liam Byrne. The right have cheerfully dug out his own contributions to the vile attempts to turn the working poor against the unemployed: “Labour is the party of hard workers, not free-riders. The clue is in the name. The party that said idleness is an evil. The party of workers, not shirkers.” Or indeed: “Let's face the tough truth – that many people on the doorstep felt that too often we were for shirkers no workers.” The grotesque sight of a Labour politician – a Labour politician – parroting the divide-and-rule bile of Tory demagogues. Not only is it shameful, it is self-defeating: there is nothing the Tories desire more than for this “debate” to be framed on their terms. They watch in satisfaction as senior Labour figures fuel the fire about “scroungers”, knowing full well that the more it burns, the broader the pool of their own potential support. The Tories have a confident, clear, consistent message; exactly what is missing from their opponents.

Thieving from the poor while turning them against each other: any response but fury at what this government is doing is inexcusable. But it is not enough. This government – a government with a flimsy, pathetic excuse of a mandate – is intolerable, and it must be stopped in its tracks. No more silent simmering with rage. Demand the Labour leadership offer an opposition worthy of the name. Expose Tory lies at any and every opportunity. Give a platform to those battered by Tory savagery. Take to the streets. Strike, and support those who do. Learn from this country's proud history of peaceful civil disobedience. Sounds too radical, too extreme, or too much like hard work? In the years to come, you will be asked what you did to stop this horror show. And if you need another incentive, picture again those baying Tories, jeering as they mugged the poor.