The drop of over £2 billion is marked by a "sharp fall" in the number of people contributing to personal (including stakeholder) pensions during the recession, as many people who had previously made small contributions stopped contributing.
The ONS report found in 2009, 56% of active members of private sector DB schemes were in schemes closed to new members, while most public sector workers can still join a DB scheme.
Darren Philp, director of policy at the National Association of Pension Funds (NAPF), said: "These trends reflect the current state of the economy and the impact this is having on UK households.
"It is understandable that people have more pressing financial priorities during difficult times, but contributing to a pension regularly is vital to ensure a decent income in retirement.
"The UK's population is on a collision course with its own retirement. People are not saving enough and millions risk facing poverty in their old age.
"The auto-enrolment reforms being introduced from next year are likely to result in 5-9 million people starting to save into a pension or save more. This is a key opportunity to get the country saving for its old age."
