Meanwhile, the study also had good news for Scotland, the foundation says that part of the UK is doing better.
According the BBC the number of jobless adults now is greater than the number of poor seniors.
The research, carried out by the New Policy Institute, suggested the number of working age adults without children in low-income households had risen in recent years, to about 220,000.
"As the rest of society has got better off, so this group has sunk ever further behind," the study said.
The study also suggested that Scotland's child poverty rate was one of the lowest in the UK.
The proportion of children living in poverty has remained at 25% for the last three years, with about 250,000 in low-income families, according to the report.
Child poverty in Scotland has fallen by a fifth since the late 1990s - similar to the reduction in Wales and some parts of the north east and south west of England.
The report said: "The reason why Scotland's performance exceeds that of great Britain as a whole is that the fall in other English regions has been negligible.
"As a result, the Scottish child poverty rate is now among the lowest of any part of Great Britain."