I received a council tax bill which someone else should pay

I've occupied a single room in this property since 2004. Over the years there have always been a varying number of other tenants in the property.According to my tenancy agreement I have always paid rent inclusive of council tax. The council tax bill used to arrive in the name of one of the tenants but obviously he never paid it and recently he moved out. From June 2010 I became the single occupier of the whole house. The council got hold of my name and sent me a bill for the past six years i.e the same bill the above named tenant didn't pay. I have written to them and explaind the situation but they answered that this has to be sorted out between me and the landlord and they would not involve. The amount is nearly £7000 and landlord wouldn't pay it either.
What can I do since I feel it is very unjust to bill me for something someone else was suppose to pay? And I do not have this amount anyway and I don't think I possess goods of this value either, so is there a solution in this case?