A motion by Labour MPs to scrap the controversial ‘bedroom tax’ fell short by 26 votes last week in the House of Commons.
East Dunbartonshire MP Jo Swinson was one of seven Lib Dem MPs who voted against the motion, helping to achieve the coalition majority.
The spare rooms subsidy has proved unpopular in East Dunbartonshire - with council chiefs and housing association bosses saying hundreds are being hit in the pocket.
The tax, introduced in April, means tenants have their benefits cut if they are deemed to have a spare bedroom.
However, a shortage of one bedroom properties has meant many are unable to move and are forced to take the drop in income.
But Ms Swinson defended the way she voted.
She told the Herald: “I didn’t support Labour’s motion because I think their position is fundamentally unfair.
“Labour are happy for the 800 families in East Dunbartonshire who claim housing benefit and rent from a private landlord not to receive any subsidy for spare bedrooms, but want a different rule for those in social housing.
“I’m focused on ensuring vulnerable people get the support they need. Following pressure from the Liberal Democrats, Armed Forces families, foster carers and families with severely disabled children will be exempt from the changes.
“The Government has also made £155million available to deal with the difficult cases.
“In East Dunbartonshire this means there is a fund of more than £250,000 to help families struggling with the changes.”
Meanwhile, the Scottish Government has supplied an additional £160,000 to top up the council’s discretionary housing payments fund.
For more information about help available to those hit by the changes call the council on 0300 123 4510.