The Government has hailed new figures showing a fall in the number of people living in poverty in recent years.
Ministers said it was "fantastic news" that one million fewer people were in absolute poverty compared with 2010.
The income gap between the richest and poorest had also fallen, with the poorest fifth of households having an extra £1,000 a year.
The official statistics showed that children were five times more likely to live in poverty if they were in a workless household.
The Children's Society said the figures also showed an increase in the number of children living in relative poverty.
Minister for family support, housing and child maintenance, Kit Malthouse, said: "It's fantastic news that one million fewer people are living in absolute poverty than in 2010, including 300,000 children.
"It makes sense that poverty rates are falling while the employment rate is increasing, and today's figures confirm that work remains the best route out of poverty.
"We know there is more to do to ensure that every child gets the very best chances in life.
"Our welfare reforms offer parents tailored support to move into work, ensuring that even more families can enjoy the opportunities and benefits that work can bring."
TUC general secretary Frances O'Grady said: "If you work hard, you shouldn't have to worry about making ends meet, but today's figures show that despite rising employment, millions of people in working households are trapped in poverty.
"Unless government reverses its planned cuts to universal credit, things will get much worse."
Children's Society chief executive Matthew Reed said: "Today's shocking child poverty figures must spur the Government into decisive action to help the 4.1 million children now living in poverty in the UK.
"Growing up in poverty can affect every aspect of a child's life: their home, health, education, family relationships and even friendships.
"These figures show the toll that systematic cuts to welfare, including the freeze on children's benefits, have taken on low-income families and the Government must now urgently review this freeze."
"We are only halfway into a four-year freeze on children's benefits that is hitting family budgets very hard. Child benefit alone will lose 23% of its value over the decade so low-income families are losing core support as prices rise."