Middle-class people consume more alcohol and illegal drugs than those living below the poverty line, according to a report by a cross-party group of academics and campaigners.

The report, compiled by the Social Metrics Commission, compared the circumstances of those living above and below the poverty line. It found two-thirds (66%) of those who are comparatively better off have drunk to excess in the last year, compared with just 58% of the most deprived. It also found 22% had taken illegal drugs, 9% higher than less well-off people.

However, the paper found that while those not living in poverty drink and take drugs more, deprived individuals experience worse physical and mental health, smoke more and have higher incidents of disability.

Two years ago Philippa Stroud, who runs the Legatum Institute thinktank, set up the commission to develop poverty measures to counteract the cost-cutting orthodoxy of the Treasury.

Stroud, who previously worked in refuges for addicts and the homeless, hoped the commission’s work would provide a tool for ministers trying to argue against spending cuts that could hit the poor the hardest.

The report, to be published on Tuesday, reveals how family circumstances are as big a driver of poverty as low income. Of lone-parent families, 52% are in poverty, compared with 25% of couples with children and one in 10 pensioners.

In 2015, David Cameron’s government scrapped Britain’s official measure of poverty, which looked only at a family’s income relative to the national average. The new measure considers household assets and childcare and housing costs, as well as the impact of disability.

The report found 14.2 million people are judged to be in poverty, a similar number to 2015. It noted that 2.7 million, largely pensioners with assets, are no longer below the poverty line, although 2.6 million – many of them disabled – whose living costs were not properly factored under the previous measure, are judged to be in poverty.

The paper also found 7.7 million people were in persistent poverty, lasting more than four years, and 8 million in deep poverty, more than 10% below the poverty line.

Those worst affected were in London, with 28% of households in the capital below the poverty line, a figure 10% higher than in some regions such as the south-east.

Stroud, a Tory peer and a former adviser to Iain Duncan Smith, worked for three years to agree the new measure with organisations including the Joseph Rowntree Foundation and independent experts such as the Office for National Statistics. It is being considered whether to adopt it as an official measure of poverty.

“We want to put poverty at the heart of government policy making and ensure that the decisions that are made are genuinely made with the long-term interest of those in poverty in mind,” Stroud told the Sunday Times.

“This new metric accounts for the negative impact on people’s weekly income of inescapable costs such as childcare and the impact that disability has on people’s needs.”

She added: “The commission’s metric also takes the first steps to including groups of people previously omitted from poverty statistics, like those living on the streets and those in overcrowded housing.

“There are some areas of good news; far fewer pensioners are living in poverty than previously thought, with a significant fall in pensioner poverty over the last 15 years.

“But compared to previous measures, it also shows that those families struggling to make ends meet because of childcare and housing costs and those who lack a financial buffer to fall back on are much more likely to be in poverty.”