hi there.
Something must be in the water as this is the second one i've looked at today.
If you are absolutely certain that it is a council mistake and that whenever a change in cicumstances happened, which may have affected the amount of benefit, they were told then you may have a claim.
Basically, If they made a mistake in the calculations and you couldn't have reasonably known about it then you could argue that you are not liable.
some councils get very shirty when they are challenged and send it straight to legal. If they start threatening you with court it may need a letter denying you owe them a debt however, make an offer to pay something each week just to keep them off your back. if you have to do this, send them a letter with the heading "I DO NOT ACKNOWLEDGE ANY DEBT TO YOU"( If anyone else has better wording, please let me know)
If they still say it's your fault, complain and escalate it to the chief executive of the housing department.
If all else fails, complain to the Local Government
Ombudsman.
NOTE: I am basing my answers on my own personal experiences with my local council and not all councils follow the same rules.
good luck
fox