UK combined defined contribution (DC) pension assets fell £18bn in October compared to the previous month, according to Aon Consulting.
The fall, to £489bn, marks the largest decrease since February, and follows a period of rallying DC assets due to stock market increases.
Earlier in the month combined DC pension assets reached a 16 month high of £520bn, hitting a level not seen since June 2008.
Volatility in the equity market means UK workers are continuing to suffer a high level of uncertainty over their pension funds.
An example 65 year old retiring on 31 October 2009 would receive an annual retirement income of £8,593, but retiring six months earlier they would have only received £7,133, a difference of over £120 every month amounting to £29,200 over the course of 20 years, according to Aon.
Richard Strachan, senior consultant at Aon says: "While October finished slightly down compared to September, the general trend for the UK's DC pension savings is on the up.
"There is still significant volatility, though, and it is vital for workers to take an active interest in their retirement savings, evaluating whether they are invested in the right funds for them, and to have some very clear goals and a strategy to achieve them."
British workers are increasingly switching their DC pensions to their scheme's default fund as a refuge from uncertainty in investment markets, according to separate research.
The majority of employers are witnessing over 80% of employees investing in the default fund, suggests the 2009 Aon Benefits and Trends Survey of employers.
Strachan adds: "In turbulent economic times, its understandable members are seeing the default fund as a safe haven. However, the security of the default fund is down to those managing the scheme. To ensure members are getting the cautious investment option they think they are, scheme investment, and the performance of default funds in particular, should be a priority for those running DC pensions."
"There is a trend towards increasing the number of investment options; however, too much choice will often lead employees to select the default option through fear or inertia. Employers and trustees need to ensure they offer an optimal number of investment choices.
To promote 'long-term investment'
Switching 'hard and expensive'
Smaller funds still packing a punch
To drive progress