Iain Duncan Smith has been accused of failing to help children out of poverty after the release of "shocking" new figures.
According to the latest data from the Department for Work and Pensions, the rate of child poverty in families with a single parent working full-time rose from 17% in 2011-2012 to 22% in 2012-2013.
Meanwhile, almost one in four children whose single parent works full-time is now growing up poor, while just under one in three with a single parent working part-time is in poverty. The rate of child poverty for single parent families (42%) is nearly twice as great as for families with both parents (23%).
Javed Khan, chief executive of the children's charity Barnardo's, said: "The news that 100,000 more children are now living in severe poverty in the UK is shocking.
"The Government is making no progress in tackling child poverty. Over the past few years, the poorest families have been left financially stranded by measures which have cut lifeline benefits, with few alternatives that make work pay, partly due to delays with Universal Credit."
Mark Goldring, Oxfam chief executive, said: "Today's figures reveal that the economic recovery is not making enough of a difference to the poorest, many of whom are facing a daily struggle to put food on the dinner table. Politicians of all parties need bolder, long-term policies that can help people move up the rungs and out of poverty.
"Whilst doing our work, we have seen the unacceptable levels of poverty that exist in one of the richest countries in the world and call for politicians of all stripes to urgently address the issues that are keeping people in poverty
Fiona Weir, chief executive of the campaign group Gingerbread, warned: "It is deeply concerning that while the economy is on the up, hundreds of thousands of families remain trapped into poverty.
“This must be a wake-up call for ministers that the attempts they are making to cut child poverty aren’t working. Cuts to financial support for both in and out of work families have instead pushed many into desperation and destitution."
However, other figures show that the number of people in relative poverty has fallen by 100,000 over the past few to 9.7 million, while the level of in-work poverty fell by 200,000.
In response, Work and Pensions Secretary Iain Duncan Smith said: "Despite the deepest debt-fuelled recession in living memory when £112 billion was wiped off the economy, we have protected the most vulnerable families from falling behind with 300,000 fewer children in poverty since 2010.
"Today's figures underline the need to stick to the Government's long-term economic plan of restoring a strong economy that creates jobs, and a tax and welfare system that helps people into work and makes work pay."
The poverty figures come as analysis from the Institute for Fiscal Studies found that the number of people below the poverty line in 2012-2013 rose by 600,000 from the previous year to 14.6 million, after deducting housing costs.
"This is about 2.0 million higher than in 2007–08," the think-tank wrote. "The difference is explained by the fact that housing costs have fallen by less for those around the poverty line than for the population as a whole – only the after-housing-costs measure accounts for this."