It is estimated that 5,000 people in Wales who are paying a spare room subsidy could - and should - have been exempt.
Under the rule, anyone who has been in their home since before 1996 and has continually claimed housing benefit does not have to pay the subsidy.
A spokesperson for the Department of Work and Pensions say they are looking at the issue carefully and will take any necessary action.
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Showers will be replaced by more persistent rain this evening, with some heavy outbreaks expected. The rain will become patchier overnight.
Mary Owen has been working at the school in Old Colwyn for 46 years and still loves her job as much now as she did at the very beginning.
The latest weather forecast for Wales.