Probation is a less well-known branch of our justice system, compared with, say, police and prisons, but that doesn't make it any less important. Hundreds of thousands of offenders each year are rehabilitated back into society by probation, which is crucial for the public's safety. That's why the government's half-baked, reckless plans to privatise and break up probation should worry us all.

Over recent weeks, as we head towards the 1 June key milestone in the government's plans this weekend, I've heard some truly alarming reports on the chaos privatisation is causing: staff shortages caused by rocketing sickness levels and dozens of unfilled vacancies are crippling the service.

As a result, a backlog of cases is building up, including offenders who have committed serious, violent crimes like domestic violence. Oversight of sex offenders has been handed to staff without the right expertise. High-risk cases aren't receiving sufficient supervision. Court reports are going unwritten. Senior management time has been sucked into restructuring, neglecting day-to-day duties rehabilitating offenders. New software designed to assess the risk that offenders pose to the public was rushed into service without adequate staff training. It is a shocking state of affairs, which could have catastrophic consequences for public safety.

It needn't be like this. No one questions the need for the probation service to reform and that more needs to be done to keep our communities safe. It's a scandal that those coming out of jail on short sentences are being left to their own devices.

We know that probation works best when the service has close relationships with the police, prisons, local authorities and health service, enabling resources to be pooled and priorities aligned around the specific circumstances of the offenders most at risk of reoffending.

Instead, what we see from the government is ideologically fuelled, evidence-free codswallop. They're heading in precisely the opposite direction, replicating the failing work programme, outsourcing service delivery to a handful of large private providers while local probation trusts are abolished and long-established working relationships ripped apart. All of this is being done without any piloting or testing to see if it works and doesn't endanger the public.

Experts – including the chief inspector of probation and even justice secretary Chris Grayling's own officials – have warned that the plans are a massive gamble. They fear that confusion caused by a lack of clear responsibility for those on probation will lead to dangerous offenders falling between two stools. What's more, the public will no longer be able to find out information on any failings and hold providers to account as most of probation will be out of scope of freedom of information laws.

None of this worries Grayling. He boasts of trusting his gut instinct over evidence. Perhaps I'm old-fashioned, but I think the need to maintain public safety demands something more than a chemical signal given off by a mix of juices in the secretary of state's stomach.

It's also unacceptable, in an election year, for Grayling to sign away a whole swath of the justice system on 10-year contracts. It's undemocratic, binding the next secretary of state, whoever they may be, to this policy and reducing their ability to choose an alternative route to reform.

I am demanding the £6bn contracts aren't signed this late in the parliament. And if agreements are made they must include get-out clauses to allow a change of government to walk away free of financial penalty. If contracts remain unsigned at the next election – and Labour wins – I will bin them. If anything is in place by May 2015, I will get the best legal minds to find all possible ways to get out of them.

Labour's alternative vision builds on strong, local, publicly run probation trusts, close to those they're supervising. Trusts have told me they'd take on supervising short-sentence prisoners within existing budgets. This makes a mockery of government claims that privatisation is necessary to free up resources to cope with prisoners serving less than 12 months.

We would set tough new targets to cut reoffending and have zero tolerance of failure. Trusts would be free to decide how to meet these targets, capturing the expertise and innovation of local charities and companies without the need for wholesale privatisation. Real change happens when the people responsible on the ground are empowered, not micromanaged from Whitehall.

The probation service has a fundamental role in keeping our communities safe. Yes, it can do better but instead of gambling with public safety, we must build on what works.