A conservative is “a liberal who has been mugged by reality”, declared the American neo-conservative Irving Kristol in 1983, as he predicted that experience would batter the idealistic into accepting the value of order and holding the guilty responsible for their crimes.

In the 21st century, it is conservatism’s turn to become unreal – and not only because Brexit has destroyed its claim to be the philosophy of the hard-headed. Brexit is a symptom of a wider Tory breakdown in which fantasies replace evidence, and temporary convenience trumps the public interest. Reality is mugging, knifing and killing the British, and all a Conservative prime minister, safe behind her bodyguards, can say is “there is no direct correlation between certain crimes and police numbers”.

Almost a decade of living with the right’s ideological preference for spending cuts rather than tax rises or counter-cyclical boosts to the economy has not just weakened the police service, but the whole public sphere. You cannot separate the two. A justice system defines a country: its levels of freedom, fear and trust. When you degrade it you degrade the whole of society.

Even if we stay within the criminal law, the consequences of the fall in police funding of 19% under the Conservatives have spread suffering far beyond the victims of crime. When they speak in private, officers from London’s shrunken murder investigation unit don’t say their greatest regret is the loss of action-man cops but of safer neighbourhood teams, which knew the streets of the capital backwards. They not only collected intelligence on criminals but also warned off children on the edge of crime – most often siblings tempted to follow their brothers into gangs. Officers were as much involved in child protection as traditional policing, and now their numbers have been reduced, children, who might have been deterred from harming themselves as well as others, are left unchecked.

Play Video 0:34 No link between knife crime and police cuts, claims Theresa May – video

The willingness of schools to exclude mentally disturbed children because they are too much trouble and drag down exam-table rankings, and the unwillingness of local and national government to fund a secure alternative, pushes many into crime. But it also hurts all expelled children, regardless of whether a gang recruits them on not.

The collapse in trust can best be seen in the crippled court system. Thousands of defendants cannot get a fair trial because they are refused legal aid, and thousands of victims never see the guilty bought to justice because the Crown Prosecution Service is a semi-derelict institution. The bureaucratic prose of CPS inspectors says prosecutors must concentrate on reducing “delays and inefficiencies in the trial process”.

Working lawyers describe the reality of court life more starkly. Simple things like ensuring that there are enough CPS caseworkers at court to attend hearings don’t happen because of lack of staff, the jobbing lawyer who writes with such aplomb under the pseudonym of “the Secret Barrister” tells me. “Phones in CPS offices ring out, their lawyers are forced to juggle more cases than they can handle, and inevitably errors creep in: failure to gather basic evidence; failure to secure the attendance of witnesses at trial; failure to disclose material which could make the difference between justice and its miscarriage.” Interpreters don’t turn up. The IT fails. A Ministry of Justice that has lost 40% of its budget prefers to let courts stand empty than meet the cost of filling them.

He defines justice in Tory England as “a system that could be deliberately designed to deter the public from using it”. A statistical measure of its detachment from the country it is meant to protect came last month when the MoJ revealed that the number of suspects the system had dealt with fell to its lowest since records began almost 50 years ago – even though recorded crime rose by more than 8% to 5m offences. Cases were collapsing because of an astonishing rise in victims and witnesses who refused to support action against suspects. Their number was up by a third in a year, to about 750,000. As drugs and weapons offences dominated the list of failed cases, Harry Fletcher of the Victims’ Rights Campaign said it was reasonable to conclude that criminals were intimidating witnesses into silence. Fear of gangsters and abusers now outweighs respect for the law.

Children, who might have been deterred from harming themselves as well as others, are left unchecked

People’s mental geography is changing as they mark out their neighbourhoods with crime scenes. In my case, I can walk out of the Observer offices and in 300 metres pass the spot where a 15-year-old died after being stabbed to death for the sake of the bike he was riding. A few days ago, a mile from where I grew up in Manchester, Yousef Makki was killed, and I won’t feel the same when I walk down that road either. Our familiarity with violence dooms “liberal” attempts to dismiss fear of crime as a “moral panic”. Diminishing crime contradicts the lived experience of millions and ignores its victims, who are likely to be poor, women, weak and/or ethnic minorities.

The low-tax consensus of the 1980s that Kristol celebrated has long gone. An ageing population meant the Conservatives paid for rising pension and NHS costs by slashing not only law and order, but defence, education, welfare for people of working age, and youth and social services. As the Institute for Fiscal Studies and many others point out, the tactic is reaching its sell-by date.

In fact, it’s past it, and this ought to be the moment when an intelligent opposition offered a coherent programme of national renewal. I am putting the case against Corbyn’s Labour at its politest when I say no such opposition exists. Our leaders may not be able to punish hundreds of thousands of criminals, but they are more than capable of locking up reality and throwing away the key. Deserving of a battering though they are, I see no prospect of it mugging them.

• Nick Cohen is an Observer columnist