Defiant peers have narrowly voted again to demand that the government drop plans to cut housing benefit for claimants in under-occupied homes.

The peers voted by 236 to 226, even though the Commons had last week rejected a similar amendment from the Lords and then imposed financial privilege, a means of preventing the Lords from tabling the same amendment again.

The Lords had opposed the so-called "spare bedroom" tax a fortnight ago, and on Tuesday reasserted that view by saying housing benefit cuts of £14 a week should not be imposed on claimants in under-occupied homes if they are unemployed, carers, foster carers, disabled or war widows.

In a process known as ping-pong, the Commons will have to address the issue again when it returns from its half-term break next week. The amendment passed was costed by the department of work and pensions as up to £100m annually by 2013-14.