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.
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The Duke and Duchess of Cambridge met young people who have battled mental health issues on Saturday.
Former Chancellor Lord Geoffrey Howe was Margaret Thatcher's longest-serving Cabinet minister, also taking on the role of Foreign Secretary.
Lord Geoffrey Howe is known by many for his resignation speech which was seen as the catalyst which destroyed Margaret Thatcher.