Thousands of families across the UK will be affected by changes to housing benefit due to come into force this week - part of the biggest shake-up of the welfare system for decades.
Ministers argue the new measures, amounting to £2.4bn in savings, are necessary, not only to tackle the rising cost of benefits and the budget deficit, but also to create a fairer system for taxpayers and to provide greater incentives for people to work.
They say expenditure on housing benefit in cash terms has increased significantly from £11.2bn in 1997/1998 to £20bn in 2009/10, and without reform they predict it will reach £24.7bn by 2014/15.
However, housing bodies and charities have warned that the changes will force thousands of poorer people out of expensive areas, such as central London, and increase homelessness.
So what are the changes to housing benefit, when will they be introduced and who will be affected?