Wales was the only UK nation to see a rise in child poverty last year, according to research by charities.
It suggested 29.3% of children were in poverty in 2017-18, a rise of 1%.
Sean O’Neill, of Children in Wales, said parents had to make “impossible choices” between feeding themselves or their children.
The Welsh Government blamed policies set by the UK government, which said it was helping families improve their lives through work.
The research by Loughborough University was commissioned for the End Child Poverty Network, a coalition of organisations which includes Children in Wales, Oxfam Cymru, Barnardo’s Cymru and Save The Children.
It suggested more than 206,000 Welsh children were living in poverty in 2017-18.
A child is considered to be growing up in poverty if they are living in a household where the income is below 60% of the median income.
It found the Cardiff South and Penarth, Cynon Valley and Rhondda constituencies had the highest proportion in Wales – all at 35% – after housing costs are taken into account.
Around a third of children living in valleys council areas like Blaenau Gwent, Caerphilly, Merthyr Tydfil and Rhondda Cynon Taf were also in poverty.
But the figures also break down child poverty into much smaller areas of deprivation, ward-by-ward across Wales.
Penrhiwceiber near Mountain Ash in the Cynon Valley has nearly half of its children in poverty, according to the research.
Three wards in Wrexham are proportionately the next worst, followed by two inner city areas of Cardiff – Butetown and Grangetown.
A snapshot of child poverty during the year suggests seven out of the 10 wards in Wales with the highest numbers of children in child poverty are in Cardiff. It estimates there are 2,342 living in Grangetown, followed by 2,183 in Ely.
Ysgol Glan Morfa is a Welsh-medium primary school in Splott, Cardiff, an area with an estimated 35% of children living in poverty. Read more