Iain Duncan Smith has confirmed that foster carers and members of the Armed Forces will not be subjected to the government's controversial so-called "bedroom tax".
From next month people renting their homes from councils or housing associations could lose some of their housing benefit if they are deemed to have more bedrooms than they need.
On Tuesday morning the work and pensions secretary said adult children who are in the Armed Forces but who continue to live with parents will be treated as continuing to live at home, even when deployed on operations.
In a written statement to parliament he also said people who are approved foster carers will be allowed an additional room, whether or not a child has been placed with them or they are between placements, so long as they have fostered a child, or become an approved foster carer in the last 12 months.
Asked by ITV News today whether his policy was unravelling, Duncan Smith replied there were "no climb-downs at all".
"This policy is absolutely vital. The last government saw many people living in accommodation they did not fully occupy," he said.
Responding to the news National Housing Federation chief executive David Orr said it the concessions should just be the start.
"Exempting armed forces personnel and giving foster carers some protection from the bedroom tax is not enough," he said.
"The bedroom tax is still an unfair and perverse tax which will hit hundreds of thousands of other vulnerable people living in social housing around the country. They are being penalised for a weak housing policy that for years has failed to build enough affordable homes and reduce the housing benefit bill."
During heated exchanges in the Commons yesterday, an irritated Duncan Smith hit back at Labour heckles over the policy by criticising their "complete lack of intelligence".
He added: "Monkeys can jump around, but the noise they make is not necessarily relevant."
Seeking to claim credit for the concessions, the co-chair of the Liberal Democrat Parliamentary Party Committee on Work and Pensions, Greg Mulholland said Duncan Smith had given into Lib Dem "pressure".
"There is a real need to deal with the chronic shortage of social housing. It is therefore important to encourage people who are under-occupying to move in to smaller accommodation to free up desperately needed family homes," he said.
"I am delighted that as a result of Liberal Democrat pressure the secretary of state has announced that families with severely disabled children who cannot share with a sibling, Armed Forces families and foster carers will now be exempt from the loss of part of their housing benefit."