Jonathan Isaby from the TaxPayers' Alliance said taxpayers would "resent" paying for spare rooms for those receiving housing benefits "when they can't have one themselves."
He said: "I'm not saying that there aren't people who do need those rooms but you can't have a blanket exemption for hundreds and thousands of people."
Campaigners against the Government's so-called 'bedroom tax' will take to the streets tomorrow in protest of the proposals.
More top news
A gunman who killed nine people and at a Munich shopping centre was German-born and had no links with Islamic State, authorities say.
Torrential rain and flooding has killed 24 people in China and forced tens of thousands from their homes, according to state media.
Police have released 12 images of people wanted in connection with what they describe as 'disorder' at a McDonalds in central London.