The figure from the Institute for Fiscal Studies debunks the myth that the majority of children who're poor have workshy parents.
The IFS also said the proportion of children living in a household where there was no one working had fallen from nearly one-in-four in 1994-95 to fewer than one-in-six in 2014-15.
Their report also said that in some key aspects middle-income families with children more closely resembled poor families in the past, with half now renting rather than being owner-occupiers.
Christian charity the Children's Society has said that low wages, insufficient working hours and benefit freezes were all contributing factors.
Speaking on Premier's News Hour David Ayre, from the charity, said: "The face of poverty has fundamentally shifted now.
"Parents are facing really difficult decisions in terms of buying their children a new school uniform, putting a hot meal on the table in the evenings or heating their children's bedrooms.
"The policy solutions and practice that we need to put in place to tackle it needs to fundamentally change."
Work and Pensions Secretary Damian Green said the report showed the Government was making progress in building "a Britain that works for everyone".
"We now have record numbers of people in work, falling unemployment and wages rising faster than inflation," he said.
"But we need to go further, which is why we have committed to increase the national living wage to benefit the poorest in society, we are taking the lowest paid out of income tax and our welfare reforms are ensuring it pays to be in work."
Listen to Premier's Antony Bushfield speaking to David Ayre on the News Hour:
