If King Herod had relaunched his career as a children’s rights activist, it would have shown no less chutzpah than the Tories have done in rebranding themselves as the party of working people.

When the Labour party was founded, more than a century ago, it emerged out of a conflict between workers wanting a better life and employers more interested in profit. When the Tories talk of standing up for “hardworking” people, they are seeking to define their interests against those of, say, unemployed people or immigrants or public-sector workers. You’re trying to get on in life, this narrative goes, but Labour is championing “skivers” or foreigners instead.

The Tory strategy is lethal because it deflects people’s legitimate anger at their problems away from the powerful, while their pockets are stealthily emptied. And that is why, whoever wins the Labour-party leadership race tomorrow, the sham of the Tories’ rebranding operation has to be exposed.

George Osborne’s announcement of a “national living wage” in the post-election budget was an audacious raid on his opponents’ territory. It exposed just how weak Labour’s election offer was: Ed Miliband championed an £8 minimum wage by 2020 as an indication of his radicalism, when this target actually belied accusations that Labour was too leftwing.

The fight for a genuine living wage is one of our generation’s most noble causes.Osborne has misappropriated the struggle and calls £9 an hour by 2020 a living wage when it is anything but. The criteria used to calculate the living wage include the in-work benefits to which low-paid workers are entitled. And it is here that Osborne is giving with one hand while taking with the other.

According to the Institute for Fiscal Studies, 8.4m working households will, on average, lose £750 from cuts to in-work support. But they will gain just an extra £200 a year from the raising of the minimum wage, leaving them £550 worse off. For some workers, the loss will be even worse. Supermarket workers, cleaners, receptionists: people who keep essential services afloat – all will be robbed. Their children will grow up in colder, hungrier worlds.

This is the reality that must be exposed by the Labour opposition. The Tories and their media allies have whipped up resentment for years over social security, telling low-paid workers that while they work all hours, their unemployed neighbours are taking the mick with supposedly luxurious benefits. Well, that whole debate needs to be urgently reframed: it is those patronised as “hardworking families” who are now being punished.

Lynton Crosby has ordered the Tories to keep religiously to the script of claiming to be the champions of working people. Labour must be equally disciplined in exposing the truth: that the Tories are driving low-paid workers further into hardship while their real base – the richest in society – thrive as never before.