Nine months ago we set out to look at the sharpest end of homelessness – not simply those who live on the streets but those who die on them or in emergency accommodation. Homelessness had become omnipresent in Britain. According to the last Shelter report, at least 320,000 people are homeless, almost 5,000 are rough sleeping (likely to be a huge underestimate) and 726 people died homeless in England and Wales in 2018 (a 22% rise from 2017). Most of those 726 would have been street homeless or in emergency accommodation.

In fact today the only way you can ignore homelessness in the UK is by averting your eyes. When, for the first time, statistics were released about the number of people who had died homeless, it was incredibly important. But we did not want these people to remain statistics. We wanted to tell their life stories, look at what went wrong and investigate what could have been done differently by statutory bodies and charities. We have told half a dozen stories so far, and there are three more to come.

When we began researching the Empty Doorway series, we knew reporting these stories was going to feel bleak, but we didn’t realise just how bleak. When we’ve not been screaming with rage, we’ve been phoning each other in the middle of the night in tears. It’s hard to get these stories – these people – out of your head. We wake up with them, go to sleep with them and often dream about them. After the tears comes the self-loathing. Who are we to be so upset? We’re not family. How can we grieve for people we never even knew? But we have found ourselves doing just that.

Yet something incredibly life-affirming has emerged too. We feared the homeless people we were writing about had died unloved and unmourned. In fact, in every case, there were loving and profoundly bereft people left behind. Cathy Teese, aunt of Aimee; Julian Humm, father of Jake; Alex Davis, sister of Kane Walker; Gabor Kasza, friend of Gyula Remes; Lee-Maria Hughes, sister of Catherine Kenny; and Saeed Fahari Alamdari, brother of Hamid – six of the most inspirational people you could ever meet.

Jake Humm. Photograph: Chris Beckr/Provided by the Humm Family

Catherine Kenny. Photograph: Courtesy of the Kenny Family

Kane Walker. Photograph: Courtesy of the Family

Aimee Teese. Photograph: Facebook

As for what we have discovered, it has been complicated, messy and repetitive. All of the people who died were addicts, and many were born into troubled families. Many might have died anyway, but every time we also came across a failing by a statutory body or charity that could have made the difference between one of these people living and dying.

It became clear, too, that there are ways to drastically reduce street homelessness and homeless deaths – changes in law, in practice, in attitudes. Yet with barely a month to go before the election, as politicians splurge out promises, none of them seem to be about this issue.

A decade ago, as mayor of London, Boris Johnson pledged to end rough sleeping in the city within three years. In 2009, he tweeted: “It’s scandalous that in 21st century London people have to resort to sleeping on the streets.” Yet since then, the figures have rocketed. Figures for 2018-19 showed that 8,855 people were recorded as bedding down on the capital’s streets last year – two and a half times the figure for 2009-10, when 3,673 were recorded as rough sleeping. This kind of increase is mirrored across the UK.

Johnson, predictably, forgot about his pledge – and the homeless. Yet his opponents, including Jeremy Corbyn, have also been muted. Yes, Labour has promised to repeal the Vagrancy Act of 1824, which makes it an offence to sleep rough or beg. And last month Corbyn made a speech in Northampton in which he said that homelessness should be recorded as a contributory factor to death, when people die on the streets.

But why is the Labour party not shouting from the rafters about the horror of homelessness? Why have they not made it the election issue? For those lucky enough not to be affected directly, “austerity” can seem like an abstract idea. But the stark evidence is there in front of us every day. When we see people sleeping on wet cardboard boxes in tunnels or shop doorways – that is austerity. Untreated addicts shooting up or smoking spice in the street – austerity. Working people living in tents – austerity. Women on the streets because the council told them they made themselves intentionally homeless for walking out on an abusive partner – austerity. Migrants, homeless because they have been denied access to public funds – austerity.

This is the austerity that victimises the poor, addicted, mentally ill, foreign, abused and vulnerable. It is a shaming reminder that Britain is not only a broken and blinkered country, it is a callous one. And for prospective prime ministers, it is a reminder of how much better we could and should be.

So what to do? First and foremost, we would like to see you, the public, saying: we are not accepting homelessness in Britain any more. Then any new government should begin with the obvious: build more social housing, ideally council housing; and properly fund a nationwide Housing First strategy. The Housing First model has been successful in places as diverse as Finland and New York. It is based on the simple principle that everybody needs a home, especially those living chaotic lives. And for those with complex needs, there is wraparound support as soon as they move in. So far, this model has been trialled in an ad-hoc, half-hearted way in this country. Often, street homeless people are told their lives are too chaotic to qualify for Housing First. And yet Housing First was devised purely for this purpose.

Time and again we have come across people who have been punished for their addictions. To throw addicts out of accommodation because they are drinking or consuming drugs is as perverse as it is cruel. In Brighton, a young man we reported on, Jake Humm, was chucked out of the YMCA for antisocial behaviour while drinking; in Harlow, physicist Hamid Farahi Alamdari was told he could only have a home if he was clean and dry. Both are now dead.

Many of the charities or private landlords tasked with housing homeless people have neither the knowledge nor the will to look after people with serious problems. An easy way to get rid of them is by enforcing “house rules”. Hostels, emergency accommodation and long-term accommodation need to be run by local (or central) government, not profit-making companies. Another problem is that the charities or private landlords providing supported accommodation are not held accountable when disasters happen. As they are classed as providing support rather than care, they are self-regulating. This meant that, although the YMCA DownsLink group knew Jake Humm was suicidal and did not check on him for at least two days after he killed himself, it did not have to answer to anybody but itself.

The YMCA DownsLink Group internal investigation concluded it followed its protocols so need not act differently if the situation were to arise again. If charities and private landlords are going to be charged with looking after the most vulnerable in society (which is highly questionable), surely they must be regulated in the same way as care providers, and held accountable for needless deaths.

Charities must also win back the trust of homeless people. Having talked to people living on the streets, it is impossible to overstate the damage St Mungo’s did to the reputation of homelessness charities after it was found to be working with the Home Office to help deport EEA nationals. The charity’s co-operation with the Home Office made many homeless people less willing to ask such charities for help.

Homelessness charities should also not be allowed to refuse to support people who are not eligible for benefits or denied recourse to public funds. The famous Connection at St Martin’s charity, which benefits every Christmas from the millions raised by BBC Radio 4 listeners, was forced to admit to us that it had denied the homeless Hungarian Gyula Remes emergency accommodation because he was not eligible for benefits. Unbelievably, The Connection reasoned that it would only be able to support him if he had a full-time job or looked likely to get one. Remes died a week after being denied access to its emergency shelter.

Then there are drugs. So many charities have told us that they can’t help addicts get clean because class A drugs are illegal. The brilliant Huggard centre in Cardiff, for instance, has a model needle exchange in which users are provided with state-of-the-art injecting packages. And yet what it really wants to be able to provide is a safe space for addicts to use. It can’t, of course, because that’s illegal. CEO Richard Edwards told us that the most it can aspire to is teaching homeless people to inject safely on the streets.

The Office for National Statistics recently reported that the number of drug-related homeless deaths rose by 55% compared with 2017. Not only that, but today’s addicts are so much more difficult to treat. Most addicts have three addictions (alcohol and at least two drugs) and there is no known detox pathway for spice, which is everywhere on the streets. Yet, even as more addicts have taken to the streets (or homeless people have become addicted on the streets) and the nature of addiction has become more complex, nearly 60% of local authorities have slashed their budget for addiction services.

There are many other simple practical ways to reduce homelessness – linking benefits to the cost of living and housing, getting rid of no-fault evictions, so dodgy landlords can’t turf out tenants after eight weeks, getting rid of the bedroom tax, scrapping the legislation that allows local authorities to refuse to support homeless people if they don’t have a local connection, making sure victims of domestic violence are housed (a third of homeless women cite domestic violence as the reason they are on the streets) rather than telling them they have made themselves intentionally homeless and throwing them out on to the streets.

Earlier this year, following the death of 31-year-old Kane Walker, Birmingham Hodge Hill MP Liam Byrne proposed introducing Kane’s Law to create a duty on public agencies, especially the DWP, the NHS, mental health and prison services, to work with councils to prevent homelessness. (He also suggested there should be reviews for everyone who dies homeless.)

Two of the women we wrote about, Aimee Teese and Catherine Kenny, died shortly after being released from prison on to the streets. Joe Anderson, Liverpool mayor, said: “I feel guilty because I manage a city council, a system, that is not joined up. It hurts. I remember David Cameron coming in and talking about the ‘big society’ – and it’s the fucking broken society. That’s what we’re dealing with. And you can’t cut and cut and cut, and not accept consequences. Aimee’s’s death is a mixture of lack of joined-up thinking and cuts. If we’d had more public health workers connecting into probation, connecting into the Prison Service, we would have been told about her”. Kenny died in Belfast days after discharging herself from hospital.

The next prime minister – whoever they are – would do well to remember Gyula Remes, who died on the streets opposite the Houses of Parliament. At the time of his death, there was an outcry from politicians – how could this happen in a civilised society? Yet 11 months on, only one thing has changed – the tunnel in Westminister leading to the Houses of Parliament, which provided people like Remes with relative warmth and security, has been shut off to rough sleepers.

• This article was amended on 19 November 2019. A sentence about the response of Joe Anderson to the death of Aimee Teese was edited to more accurately reflect the statement he made.