Cost of living: In work poverty growing, Foothold Cymru warns
"People are working hard and still can't make ends meet."
Mike Theodoulou said "in work poverty" was the worst he had seen in the 25 years he has been running Foothold Cymru, which helps to feed 600 families a week in Carmarthenshire.
"The hidden poverty in our communities is horrendous," he said.
The Welsh government said it had committed more than £1.6bn on schemes to target the cost-of-living crisis and "put money back in people's pockets".
Meanwhile, Chancellor Kwasi Kwarteng has said more tax cuts were on the cards following criticism that Friday's mini-budget would benefit the richest in society.
It comes as experts from the Wales Centre for Public Policy said poverty in Wales was being deepened by rising costs, high inflation and the price of energy.
Mr Theodoulou said demand for help from families was "going through the roof".
"What we are seeing is people queuing outside our community food shops, waiting for us to open so that they can get subsidised food to put on the table," he told BBC Radio Wales Breakfast.
"The difficulty that we've got is the connection between struggling, poverty and suffering and mental health, is huge."
Mr Theodoulou said the charity helped a vulnerable man who had not eaten for three days and whose lights had been switched off.
"He used to be looked after by his sister but his sister was hospitalised and nobody knew that this person was suffering," he said.
"Luckily, the neighbours found out and we intervened but the hidden suffering that is going on at the moment is horrendous."
Dan Bristow, a director at Wales Centre for Public Policy, based at Cardiff University, said people were really struggling.
It has suggested greater collaboration between organisations working separately to provide support after being commissioned by the Welsh government to look at how best to help people who are struggling.
"While the Welsh government and Welsh public sector are really active across a range of different areas to try and support people in different ways, actually, those interventions to support people aren't particularly well joined up around the people they are trying to support," he said.
The Welsh government said: "Tackling poverty cannot be seen as a singular issue and that is why we take a government-wide, long term approach in Wales.
"This year alone we have committed to spend more than £1.6bn on schemes that target the cost of living crisis and on programmes that put money back in people's pockets."