The new child poverty statistics, covering the first year of the recession, 2008-2009, were published on Thursday – to no fanfare at all. Perhaps that is because with Iain Duncan Smith now installed at the Department for Work and Pensions (DWP), there was no desire to highlight what was expected to be strong evidence of success at last for Labour's child poverty strategy.

What the figures actually show is something quite different – and much more unsettling. Certainly, for the first time in four years, the headline child poverty statistic ("the number of children living in households with an income less than 60% of median income in that year") came down, albeit by the smallest amount the DWP is prepared to report, namely 100,000.

To have reversed the steady upward climb of recent years, especially in a recession, is a success – but it has come at a price.

Between April 2008 and January 2009, Labour threw an awful lot of money at the problem. The result was that following two rises in child benefit and the biggest rise in child tax credit since it was introduced in 2003, an out-of-work family with two children was more than £600 a year better off at the end of the year than it had been at the beginning.

With several hundred thousand children belonging to families just a few pounds a week below the poverty line (which, incidentally fell slightly in value year on year on the more sensible "after housing costs" basis) this big increase – larger than the previous three years put together – was likely to have a positive effect, even after allowing for the recession. And so it has proved, the number of children in poverty in workless households having come down year on year by 200,000.

By contrast, the number of children in poverty in working households went up. In part, this is the effect of the recession. The employment statistics show a big increase in part-time working, and it is such part-working families – where either no one is working full-time or where one adult is staying at home – that are usually the ones who are both in work and in poverty.

The recession, though, is only part of the story here. With the exception of New Labour's five golden years starting in 1999, in-work poverty has been on a rising trend since at least as long ago as the late 1970s. It was the return to rising in-work poverty after 2004-05 that destroyed Labour's goal of halving child poverty by 2010.

The way the DWP reports this statistic, six in every 10 children in poverty now belong to a working household. This proportion is broadly similar for the 7.8 million working-age adults in poverty. The increase in this number over 10 years, of 1.1 million, would be seen as a huge policy failure had the previous government ever shown the slightest interest in adults without children.

And perhaps this in truth is why the DWP has said so little about these figures. For it suits politicians of all parties to claim that work is the route out of poverty. Such a message wraps a snarling toughness directed at workless adults inside a saccharine justification: you must work for the sake of your kids.

The truth is very different. Work that does not provide a sufficient income is now much more to blame for poverty than worklessness. If the new government is serious about poverty reduction, it will need to direct its reform efforts not just at the world of welfare but at the world of work, too – starting with the public sector.