A joint study by charity Action for Children and the End Child Poverty campaign shows the number of children has risen by five per cent, from 12,325 to 15,352, from 2014/15 to 2019/20.
The research carried out at Loughborough University takes into account housing costs and household incomes, estimating numbers of children living in homes which have below 60 per cent median incomes.
Barnsley is 32nd out of 382 local authority areas when the percentage rise is taken into account, but the borough’s figures closely follow a rise across Yorkshire and the Humber, where average rates have increased from 28 per cent to 33 per cent.
Imran Hussain, director of policy and campaigns at Action for Children, said: “These deeply worrying figures reveal the true extent of the hardship facing families across Yorkshire and the Humber - even before the pandemic hit.
“With child poverty rates rising, children in the region are among those most exposed to the devastating economic consequences of the pandemic.
“We are desperately concerned this generation of children have had their childhoods and life chances damaged and disrupted by poverty and the pandemic.
“If the government truly wants to level up parts of the country hardest hit by poverty, they must scrap their plans to cut Universal Credit later this year and give families a fighting chance at recovery.”
Coun Trevor Cave, Barnsley’s cabinet spokesperson for children’s services, said: "Evidence tells us that the number of families living in poverty in Barnsley is higher than the national average.
“We know how living and growing up in a household affected by poverty disadvantages children and families.
“It limits children's opportunity to reach their full potential, and it disadvantages families from generation to generation.
"So that Barnsley is the place of possibilities for everyone, we're working with our partners to support our children, young people and their families.”
Coun Cave referred to a report due to be presented to cabinet from Barnsley’s overview and scrutiny committee, which ‘sets out several recommendations to inform the borough’s plans to tackle child poverty locally’.
Contributors to poverty are not solely financial and a number of measures - including improving access to health and wellbeing services, training and work in schools to ‘promote ambition’ - are on the agenda.
“This will be used to enhance our current approach and help us to build back better as we move on from the pandemic,” added Coun Cave.
Barnsley Central MP Dan Jarvis called the figures ‘shameful’.
"Four years on from my Private Members' Bill to tackle child poverty, the situation is getting worse on the Tories' watch,” he added.
"The Government have a moral responsibility to ensure that where you grow up doesn't determine where you end up."
Barnsley East MP Stephanie Peacock said: “In one of the richest countries in the world, no child should grow up in poverty.
“These appalling figures demonstrate exactly why we cannot rely on rhetoric.
“The last Labour government took nearly a million children out of poverty. Under the Tories that has been reversed.
“With one in three children in Barnsley now growing up in poverty, we need bold action and investment from Government in our communities and early years.
“Families across Barnsley deserve better than this.”