Figures from consulting group Rubicon show that pension funds had their worst month for more than five years in January, with the average fund down 6.7% in the month.
This came as worries about a US recession led to further volatility on world stock markets.
Irish pension funds have now lost 10% of their value over the past 12 months. Friends First delivered the weakest monthly performance, down 7.7%. Canada Life/Setanta suffered least, losing 5.2%.
