David Cameron has moved to combat church leaders' attacks on his welfare policies by agreeing a redefinition of what constitutes child poverty and introduce new measures to combat it.

In what is certain to prove a hugely-controversial policy, it is reported that the prime minister has given work and pensions secretary Iain Duncan Smith the green light for the reform, over-ruling some objections from ministers said to include chancellor George Osborne.

Duncan Smith originally proposed a change in the way child poverty is calculated more than two years ago but his proposals have been bogged down in a review and internal cabinet battles, with fears they would be seen by Labour as a way of artificially lowering figures.

The government promised to end child poverty by 2020 but has no prospect of meeting the target so, critics claim, is ready to "fiddle the figures".

The recent attacks on the government's benefits reforms by Cardinal Vincent Nichols, followed by other faith leaders, has pushed the government onto the defensive over welfare in general and Duncan Smith's reforms in particular.

The minister, however, is said to be annoyed that he is being portrayed as favouring punitive measures when he actually wants to help the worse-off with better-targeted benefits, while removing incentives to claim welfare by those able to work.

His supporters insist he is not interested in massaging figures but understanding and responding to the reality of poverty so he can better target it, rather then relying on a measure that is no longer adequate.

But unless he can provide concrete measures with easily understandable and measurable poverty figures that can be compared to the existing ones, there will be suspicions this is a cynical political tactic.

At the moment children are reckoned to be living in poverty if they are in a family with an income less than 60% of the median household income.

But Duncan Smith believes that is too imprecise a measure and he is believed to favour wider measures to include access to good education, decent home life, the impact of drug or alcohol abuse, and whether there is persistent unemployment.

He wants to target measures on such families said to include extending free school meals, reducing energy bills by £50, extending the warm home discount, reducing water bills and lowering food bills through vouchers.

It is unclear whether the proposals are to be unveiled later this week, or will actually include a new definition of child poverty.

But it appears Cameron has stepped in to end any delays and that an announcement from Duncan Smith is imminent.