This could be the day the dam breaks – the day that collapses what’s left of the Tory party, which on Wednesday night found itself embroiled in another hasty rearranging of the cabinet after the firing of defence secretary Gavin Williamson. Today the country may finally rebel as people get out there and vote against a near decade of senseless slash and burn. Enough.

The conventional complaint is that people voting today will not cast their ballot on the quality of their local authority services, but lazily use it as a vote on national politics. Please, begs the Westminster government, judge your council not us. But that has become an absurdity. The government has cut councils so close to the bone that there is less and less difference between their political complexions on the ground: Labour and Tory councils alike struggle to cover their barest statutory duties to safeguard children at risk and care for the frail elderly, with little leeway to choose other political priorities.

That means that what matters in council and mayoral elections today is how to stop this Conservative government destroying what’s left of local government, as cuts are planned to keep raining down until 2024. The only vote worth casting locally is one that does maximum damage to the Conservative party at Westminster, because that’s where the fate of the local is decided now.

At the Tory conference just before the coalition took power in 2010, at a small fringe meeting, I eavesdropped on a soon-to-be cabinet minister (Francis Maude, since you ask) laughing to a colleague that they were all for devolution, especially for “devolving the axe”. And so they did, local government taking one of the heaviest hits and all the blame. Grants have been cut by 50%, to be zero by 2022. Voters see council tax rising this year as services are cut again – and this is the only actual tax bill most people see, so it’s disproportionately resented. Many more of the poor pay as their council tax subsidy is cut, so debts build up and bailiffs knock for this poll tax by the back door.

As the axe fell, at first councils had political choices on what should go first – libraries, pothole repairs, children’s centres, youth workers, social workers or day centres. Tory councils might choose to keep council tax low: that’s how Northamptonshire went bust. Labour councils tried to hold on to Sure Start for a while. But after nine years of the axe, there are precious few choices. Large swathes of the old and frail now get no care. The Commons select committee on local government this week revealed gross neglect in children’s services, numbers taken into care doubling due to lack of early family support. Occasional examples of excellent programmes survive – the Guardian reported this week on Labour-held Leeds’s success with a child obesity project. But mainly it’s firefighting: the political decisions are all about which fire is most urgent.

The prime minister tells bare-faced lies about funding, blatant and breathtaking. In a reply to Jeremy Corbyn, she told the Commons: “We are making more money available for local authorities to spend.” Yes, a rise of 0.8%, all of it ringfenced for the elderly, meaning everything else is cut again. But the population is rising every year, with the numbers of old people needing care rising steeply. That’s not a “real” increase but a cut. Care homes relying on state-funded residents are going bankrupt, the huge Four Seasons collapsing this week, while Health Investor reports this week, “the self-pay care home market booms”. No promised green paper on paying for social care emerges.

Councils have failed to protest: Tory authorities kowtowing to their government, leaders awaiting their knighthoods, deserve their comeuppance today. The Local Government Association has been Tory-run since 2010, making only tepid objections. Labour councils at elections feel they must show how well they have done despite cuts: indeed, Labour districts are better run than ever, with skilful leaders from Newcastle to Leeds and Liverpool, Barnsley to Camden and Reading. But it’s hard to win elections by admitting your services are declining.

Besides, how can voters judge their councils? There is little local media to report councils seriously. What do most voters know, beyond the few visibles – the potholes, lighting, bin collections and libraries? Most council spending goes on a small minority of constituents – the expensive children’s and elderly services – whose quality few ever see. Unless there is a Baby P scandal, who knows? The elderly may die alone at home without care: Age UK reports that 54,000 have died waiting for care packages in the 700 days since the government first said it would publish a care green paper.

Local election aficionados Profs Colin Rallings and Michael Thrasher predict a Tory thrashing. One Tory analyst, the peer Robert Hayward, expects Tory losses of more than 800 councillors. Brexit will sway turnout and votes either way, Labour losing remainers, Tories losing leavers. John Strafford, the chairman of the Campaign for Conservative Democracy, tells the Financial Times that in at least half of parliamentary seats there are now fewer than 10 activists left: this is a dying party, deserving of a coup-de-grace.

Whether your concerns are local or national, only one thing really matters today. The Tories deserve the kind of life-threatening loss from which they might never recover, for their deliberate destruction of local government. Wherever you vote, choose the party with the best chance of punishing Tory councils. In some places that might be Labour: in Dudley, Labour is only one seat behind the Tories. But in others, the challengers will be Lib Dems: in Winchester they are only one seat behind the Tories. Get out there and vote down the party that has done historic, monumental, irreparable damage to the country, locally and nationally.

• Polly Toynbee is a Guardian columnist