About 9,800 households in Caerphilly County Borough have no working occupants, according to official figures.
Data from the Office of National Statistics show that 17% of the area’s households were workless last year, slightly higher than the UK-wide average of 14%.
Across Wales, this figure was 17%. The ONS classes households as workless if no one aged 16 and over living there is employed.
While figures were not broken down locally, the most common reason people gave for not being in employment across Wales was sickness or disability – cited by 38% of those out of work.
Students made up 13% of jobless people, and early retirees 12%.
Only 11% of the group were officially unemployed, or looking for work and able to start within two weeks.
According to the Department for Work and Pensions, the number of workless households has fallen in all parts of the UK since 2010, with more than one million households with at least one adult in work.
A DWP spokeswoman said: “We are committed to ensuring this trend continues by supporting people, especially parents, into work by providing personalised support through our job centres and under the new benefits system parents can claim up to 85% of childcare costs.”
But this has masked an “explosion” of insecure work pushing people into the red, said Trades Union Congress general secretary Frances O’Grady.
She said: “Any drop in unemployment is good, but it’s not right that millions of hard-working people across Britain are struggling to make ends meet.
“And if the Government presses ahead it with its threat of a no-deal Brexit this will only get worse.”
Unions were key to negotiating better conditions and pay in the workplace, Ms O’Grady added.
Mike Hawking, policy and partnerships manager at the Joseph Rowntree Foundation, welcomed the rising employment rates, but cautioned that more working families were being “trapped in poverty”.
He said: “Low pay, low skills and a lack of good jobs in large parts of the country are holding people back from a decent life.
“People on low incomes are frustrated at the lack of action to improve their living standards and are demanding change.”
Mr Hawking called on policymakers to “right this wrong” through social security reform and investing in overlooked towns and cities.