The UK government has inflicted “great misery” on its people with “punitive, mean-spirited, and often callous” austerity policies driven by a political desire to undertake social re-engineering rather than economic necessity, the United Nations poverty envoy has found.

Philip Alston, the UN’s rapporteur on extreme poverty and human rights, ended a two-week fact-finding mission to the UK with a stinging declaration that levels of child poverty were “not just a disgrace, but a social calamity and an economic disaster”, even though the UK is the world’s fifth largest economy,

About 14 million people, a fifth of the population, live in poverty and 1.5 million are destitute, being unable to afford basic essentials, he said, citing figures from the Institute for Fiscal Studies and the Joseph Rowntree Foundation. He highlighted predictions that child poverty could rise by 7 percentage points between 2015 and 2022, possibly up to a rate of 40%.

“It is patently unjust and contrary to British values that so many people are living in poverty,” he said, adding that compassion had been abandoned during almost a decade of austerity policies that had been so profound that key elements of the postwar social contract, devised by William Beveridge more than 70 years ago, had been swept away.

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In an excoriating 24-page report, which will be presented to the UN human rights council in Geneva next year, the eminent human rights lawyer said that in the UK “poverty is a political choice”.

He told a press conference in London:

Austerity Britain was in breach of four UN human rights agreements relating to women, children, disabled people and economic and social rights. “If you got a group of misogynists in a room and said how can we make this system work for men and not for women they would not have come up with too many ideas that are not already in place,” he said.

The limit on benefits payments to only the first two children in a family was “in the same ballpark” as China’s one-child policy because it punished people who had a third child.

Cuts of 50% to council budgets were slashing at Britain’s “culture of local concern” and “damaging the fabric” of society.

The middle classes would “find themselves living in an increasingly hostile and unwelcoming society because community roots are being broken”.

The government said it “completely disagreed” with Alston’s analysis. A spokesperson said household incomes were at a record high, income inequality had fallen and that universal credit, which Alston attacked as “Orwellian” and “fast falling into universal discredit”, was supporting people into work faster.

“We are absolutely committed to helping people improve their lives while providing the right support for those who need it,” the spokesperson said.

Alston’s report follows similar audits of extreme poverty in China, Saudi Arabia, Ghana, Mauritania and the US. Donald Trump’s White House administration launched a furious response after the US was accused of pursuing policies that deliberately forced millions of Americans into financial ruin while lavishing vast riches on the super-wealthy.

Charities working to alleviate poverty said the report on the UK was a “wake-up call for government”.

It is likely to crystallise growing public unease over the impact of nearly a decade of cuts to the welfare state and public services, which studies have shown have had a disproportionate effect on the poor, the disabled and women. Soaring use of food banks, increasingly visible homelessness and cuts to school budgets have widened concerns about the Conservative party’s fiscal strategy.

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After visiting towns and cities including London, Oxford, Cardiff, Newcastle, Glasgow and Belfast, Alston said that “obvious to anyone who opens their eyes to see the immense growth in food banks and the queues waiting outside them, the people sleeping rough in the streets, the growth of homelessness, the sense of deep despair that leads even the government to appoint a minister for suicide prevention and civil society to report in depth on unheard-of levels of loneliness and isolation”.

He called for the elimination of the five-week delay in receiving benefits under the universal credit system, which has plunged many into destitution. Flaws in its design and implementation harmed claimants’ mental health, finances and work prospects, and benefits sanctions were “harsh and arbitrary”. Vulnerable claimants “struggled to survive”, he said.

The ministers he met – including Esther McVey, who was the work and pensions secretary until Thursday, when she resigned over the Brexit deal – were almost entirely dismissive of criticisms of welfare changes and universal credit, he said. Instead, they described critics as political saboteurs or said they failed to understand how it worked.

He highlighted the chancellor’s decision in this month’s budget to give a tax cut to the rich rather than using that money to alleviate poverty for millions, adding: “Austerity could easily have spared the poor, if the political will had existed to do so.”

Alston said the government was in a state of denial and there was a “striking disconnect” between what ministers said and the testimonies he heard from ordinary people.

“Even while devolved authorities in Scotland and Northern Ireland are frantically trying to devise ways to ‘mitigate’, or in other words counteract, at least the worst features of the government’s benefits policy, ministers insisted to me that all is well and running according to plan.”

He said he had met people who did not have a safe place for their children to sleep, people who had sold sex for money or shelter, young people who felt gangs were the only way out of destitution, and people with disabilities who were being told they needed to go back to work or lose support, against their doctors’ orders. He described how town hall budgets had been “gutted” in England resulting in a record sell-off of libraries and parks and closures of youth centres.

“I have also seen tremendous resilience, strength and generosity, with neighbours supporting one another, councils seeking creative solutions and charities stepping in to fill holes in government services,” he said.

On food banks, he said: “I was struck by how much their mobilisation resembled the sort of activity you might expect for a natural disaster or health epidemic.”

A common theme of the testimonies he heard was the impact on people’s mental health and feelings of loneliness and fear. “I was surprised by the talk of suicide, by the people I met who said they had considered suicide … There are some pretty serious mental health dimensions.”

In his conclusion, Alston called for “the legislative recognition of social rights” in the UK, a move that has long been resisted by UK governments but which is the status quo in countries such as Sweden and Germany.

Margaret Greenwood, the shadow work and pensions secretary, said: “The government should listen to the people being pushed into poverty by its policies. Universal credit is failing miserably, leaving families in debt, [in] rent arrears and at risk of becoming homeless. Three million children are growing up in poverty despite living in a working household.

“Labour will stop the roll-out of universal credit, end the benefit freeze and transform the social security system so that it supports people instead of punishing them.”

The evidence: what Alston heard on his UK visit

Universal credit has punched us in the face. Before much longer people will turn to crime. People will smash the windows to get what they want. This is going to cause riots – Denise Hunter, 57, at the West End food bank in Newcastle-on-Tyne

I got hungry because I was smelling the other food. I had to take my eyes away from it. The most unfair thing is the government knows families are going through hard times but they decide not to do anything about it – John Adebola-Samuel, 12, whose family couldn’t get school meals in Dumfries, Scotland, because of their immigration status

I wash in what I call a birdbath – a little hot water in a basin and have a spruce down. To keep warm I wrap up in layers and layers. I never thought I would be 48 and in this position – Sharon Morton, 48, at Newcastle Citizens Advice Bureau

If people don’t have enough space at home, you need to be outside and you are exposed to the big world and all sorts of people and pick up bad habits. Anyone offering them a way of making money, they will take it. That’s why I think drugs and crime are on the increase – Sahra Roble, 19, from South Acton in London

I was 18 [and homeless] and the council said I was not a priority. I was struggling with depression and anxiety and juggling work. I was told that if I stop work and have a baby I would be more likely to get housing – Tayah, west London

• This article was amended on 19 November 2018 to clarify that child poverty has been forecast to rise by 7 percentage points, not 7%, between 2015 and 2022.