David Cameron is looking to revive plans to change the way that child poverty is measured, in advance of figures that are expected to show it has increased for the first time in a decade.

The prime minister discussed the matter with the cabinet on Tuesday morning, Downing Street confirmed, with Nicky Morgan, the education secretary, Oliver Letwin, the Cabinet Office minister, and Iain Duncan Smith, the work and pension secretary, leading a conversation on whether the government was using the “right” measures.

The current definition of child poverty is whether a child lives in a household with an income less than 60% of the national average. Cameron’s official spokeswoman pointed out that this means fewer children could be in poverty during a recession because average household incomes have fallen, even if their circumstances stayed the same.

The issue was considered two days before official Below Average Income statistics are published, with the Institute for Fiscal Studies forecasting an increase from 2.3 million to 2.5 million children in poverty – the first rise for 10 years. When the figures are released, the government is expected to argue they are not a true reflection of poverty and should be changed. But Cameron may not want to risk accusations that he is trying to dodge his record on child poverty by making an official announcement on changing the measurements on the same day.

You can’t have one nation if children’s opportunities and life chances at every turn are shaped and limited by poverty Alison Garnham, Child Poverty Action Group

One option could be to supplement the current definition with new ones, rather than replacing it altogether. Changing the definition of child poverty was discussed under the last government but then put on hold in 2014, as the coalition could not agree how it would be done. The measure under consideration would have taken a complex approach that also took into account whether children have access to a good education, a decent home, and a stable family.

A little-noticed line in the Conservative party’s general election manifesto said the government would “work to eliminate child poverty and introduce better measures to drive real change in children’s lives, by recognising the root causes of poverty: entrenched worklessness, family breakdown, problem debt, and drug and alcohol dependency”.

In a speech on Monday about welfare and opportunity, Cameron gave a strong hint that proposals to change the definition were back on the table. “Just take the historic approach to tackling child poverty,” he told the audience in Runcorn. “Today, because of the way it is measured, we are in the absurd situation where if we increase the state pension, child poverty actually goes up.”

The No 10 spokeswoman said ministers had talked about how they would deliver on the manifesto and had considered “how to have the right measures in place to drive real change to tackle the root causes of poverty”. “Some of this ties in with the argument the prime minister was making [on Monday]. He wants the government to focus more on tackling the causes of the issues, rather than just treating the symptoms.”

Asked whether Cameron is unhappy with the current definition, she said: “He did point to concerns, and this was something talked about in the manifesto, about whether it is an effective measure or not, because if you look at the recession, the measured rate of child poverty fell because, actually, overall people’s income in the UK was falling, and child poverty was therefore seen to have fallen because it is a relative measure.”

Critics argue the government’s welfare changes are likely to make child poverty even worse, especially if, as expected, the plan to reduce the budget by £12bn includes a large cut to tax credits.

Alison Garnham, chief executive of Child Poverty Action Group, said no moral mission such as that described by Cameron “involves taking away tax credits for our poorest children, [and] no serious plan for the low-paid begins with making them poorer by cutting their tax credits”.

“You can’t have one nation if children’s lives, opportunities and life chances at every turn are shaped and limited by poverty. The government’s child poverty approach is failing but the prime minister’s speech simply missed the point and failed to set out what his government will do to prevent his legacy being the largest rise in child poverty in a generation,” she said.

“It is no good pulling bodies out of the river, without going upstream to see who is throwing them in – especially, if turns out the culprit is government policy. The right choices that would reduce poverty include protecting children’s benefits with the same triple-lock protection pensions enjoy, fixing the deep cuts to tax credit help for the low-paid, tackling cripplingly high rents, high childcare costs and expanding free school meals.”

The Fabian Society has also warned that “significant cuts to tax credits will lead to higher child poverty and worse life chances for young people from disadvantaged homes”.