Nearly a third of all families working part-time in Wales live in poverty, compared to 7% for full-time working families, according to research by the Joseph Rowntree Foundation.
The Monitoring Poverty and Social Exclusive in Wales 2013 report, which covered the three years to 2012, revealed that almost 700,000 people in Wales live in poverty - nearly a quarter of all people in the country.
The research, which was conducted by the New Policy Institute (NPI) and the JRF, found that 51% of working-age adults and children in poverty in Wales are from working families.
"This report shows there are not enough jobs, not enough hours and not enough pay for people in Wales," says Director of the NPI Peter Kenway.
"These are families who are going out to work but still have so little they are living below the poverty line and struggling to make ends meet."
Meanwhile, a quarter of employees earning less than the Living Wage of £7.45 per hour are in poverty, compared to only 3% of those earning more.
In the region, over a quarter of the working-age population was economically inactive in 2012 - higher than the British average by almost 3.5%.
Aleks Collingwood, policy and research manager at the JRF, says: "The Welsh government deserves credit for its Tackling Poverty Action Plan, but it must address low pay as well as low hours."
The report also highlighted the regional differences of both in-work and out-of-work poverty across Wales.
According to the report, the west and north west of Wales own the largest share of working families that are living in poverty, signalling that the rural areas are the worst affected.
Vaughan Gething, the Welsh Government's deputy minister for tackling poverty, said he was unsurprised by the study's findings.
"Most people want to work rather than live on benefits and will take lower paid or part-time jobs rather than be unemployed," he says.
"We are committed to taking action that helps lift people out of poverty and into work."
A spokesperson from the Department for Work & Pensions told IBTimes UK that "we remain committed to making work pay and our welfare reforms will improve the lives of some of the poorest families in our communities."
"The Universal Credit scheme will further increase work incentives making three million households better off and lifting up to 250,000 children out of poverty."