On Tuesday, the chancellor announced that the government’s debt would start to fall relative to GDP – a target originally set by George Osborne in 2010. Back then, the then chancellor said “We’re all in this together”, while in 2012 his chief secretary to the Treasury, Danny Alexander, told delegates at the Liberal Democrat conference: “We simply will not allow the books to be balanced in a way that hits the poorest hardest.” On Wednesday, the Equality and Human Rights Commission publishes our research, which contains the most detailed and thorough assessment yet of those claims.

Our analysis shows that, contrary to Alexander’s pledge, changes to taxes and welfare payments since 2010 have indeed hit the poorest hardest, whether you look at the record of the 2010-15 coalition government or that of the Conservative government elected in May 2015. Some changes, such as increases in the personal allowance and the minimum wage, have boosted incomes; but others, especially cuts to benefits and tax credits, more than offset this.

Looking both backward and forward, by 2021-22 the overall impact of all these changes will have been to reduce the net incomes of the poorest fifth of households by about a tenth, on average, while making little or no difference to the incomes of the richest fifth.

The precise mix of reforms was a political choice. It was not inevitable that the most vulnerable would bear the brunt

But it’s not just about whether you’re rich or poor. The pain is spread unevenly between men and women, and people of different ethnicity. Women lose more than men – especially single parents, whether they are in or out of work. The average lone parent family will lose a fifth of their net income. Pakistani and Bangladeshi households, which tend to have lower incomes and to have more children, also suffer a double whammy. And disabled people are very hard hit, particularly those with more severe disabilities. Households with both a disabled adult and a disabled child will lose, on average, about £6,500 a year.

Perhaps the most harmful of the benefit cuts is the four-year freeze in most working-age benefits and tax credits. But the reduced generosity of universal credit, whose original intention was to improve work incentives and family incomes, now means that it will penalise those it was intended to help.

The two-child limit for benefit payments hits larger families. And the changeover from Disability Living Allowance to Personal Independence Payment will hit people with severe disabilities – although the government’s decision to accept the recent court ruling that all claims should be reviewed, and reassess many of those affected, is likely to mitigate these impacts.

The changes hit lower-income families with children the hardest, and so the likely result will be a sharp increase in child poverty – we estimate, over the next five years, an extra 1.5 million children in poverty, an increase of more than 10 percentage points.

Q&A How do poverty levels in the UK compare with other countries? Show The main poverty indicator used in the Joseph Rowntree Foundation's study is the number of households that have income levels of less than 60% of median income. Using the same measure, the UK was ranked 22nd out of 35 in an international league table of child poverty rates in rich nations put together by Unicef in 2012. In a 2016 league table of all measures of poverty, the UK did rather better compared with other nations. The study, also by Unicef, ranked the UK joint-14th out of 35 rich nations. This was just above the US, but well below many European countries, notably Denmark, Finland and Norway. On some specific measures the UK did less well, notably education, where it ranked 25th out of 39 countries, and health, where it was 19th out of 35. In the latest official comparison of poverty across the 28 countries in the European Union, the UK ranked 15th. This was some way behind the Czech Republic, Sweden and the Netherlands but ahead of Ireland, Spain and Italy. The European figures confirmed the JRF’s observation that the number of people at risk of poverty in the UK has risen since 2008.

Osborne’s plan to reduce the deficit while cutting taxes for some inevitably implied major changes to the tax system, and cuts in benefits. But the precise mix of reforms implemented was a political choice, and it was certainly not inevitable that it would be the most vulnerable groups that would have to bear the brunt. Before making such changes, the Treasury should carry out – and publish – exactly the sort of analysis we have undertaken, precisely so that these impacts can be anticipated and mitigated. The government’s recent race disparity audit shows that civil servants are more than capable of doing this, if the political will is there.

Our analysis shows that if the government continues the current trajectory, Osborne’s claim that we are all in this together will ring ever more hollow. On current plans, the next few years will see very substantial further cuts to the levels of welfare benefits, pushing more children into poverty and further disadvantaging the very groups – people with disabilities, certain ethnic groups, women and lone parents – that are already relatively worse off. A rethink is long overdue.

• Jonathan Portes is professor of economics and public policy at King’s College London. This article was co-authored with Howard Reed, director of Landman Economics.