A union has called for tougher laws to make local authorities collect all rents and taxes that they are owed.
The GMB is concerned about uncollected council tax and rent
New research shows that local authorities in England failed to collect £835m in taxes and rent in the 2003/4 financial year, says the GMB.
Councils should have more powers to make landlords responsible for ensuring that tenants pay council tax, it says.
The union suggests that the extra revenue could be used to help guarantee the pensions of council workers.
The GMB says a survey of 354 English local authorities shows that uncollected tax amounted to £581m, while uncollected rents totalled £253m.
The research places Birmingham at the top of the list, with £26m in uncollected revenue. The inner-city London boroughs of Hackney and Lambeth followed closely behind (with £24m, and £22.3m respectively) and Manchester was fourth, with £17.7m in uncollected revenue.
Commenting on the findings, a GMB official, Justin Bowden, said: "If councils could collect the monies they are owed, they could easily fix the pension gap problem."
The GMB has been a leading member of the campaign to safeguard pensions, including those of public sector workers.
The pensions crisis facing Britain's workers was exposed last autumn, when a government-appointed commission chaired by Adair Turner reported that there was a huge shortfall, and highlighted the need for more spending on state pensions and more savings by individuals.
Raising the state pension age was one of the possible solutions put forward by Mr Turner. The commission's final report will be released in the autumn.