Less than half of all employees in Ireland were saving towards a pension last year, according to the Central Statistics Office.
Its survey of pension coverage in the third quarter of 2018 found that 47.1% of all people in employment were contributing towards a private pension.
That is up 0.4 percentage points on the same period of 2015.
When pension coverage from previous employments, as well as deferred pensions and pensions in draw-down mode, are included the ratio of those covered rose to 56.3%.
The CSO found that just 16.3% of people aged 20-24 were contributing to a pension, compared to almost 71% of workers aged 45-54.
Meanwhile the data shows that more than half of all self-employed people had pension coverage.
The Irish Congress of Trade Unions said the figures highlighted the need for pension auto-enrolment as part of a wider reform of the system in Ireland.
"Tax relief has failed as a policy instrument for encouraging low and middle-income earners to save enough towards a financially secure retirement, and there is no legal obligation on an employer to provide or contribute to a pension scheme for employees," said ICTU's social policy officer Dr Laura Bambrick.
"As the State pension is paid at a flat-rate, rather than earnings-related, workers without retirement savings are exposed to a significant drop in their living standards in old age."