Hull North MP Diana Johnson has slammed this week's "two-faced" Lib Dem behaviour over the Bedroom Tax.
On Wednesday, the President of the Lib Dems said that their party was withdrawing support for the Bedroom Tax.
Then, on Thursday, 46 Lib Dem peers voted in the House of Lords against a Labour motion against the Bedroom Tax. The motion was lost by 173 votes to 188 only 15 votes.
Diana Johnson MP said: "Only 24 hours after Lib Dems said they were withdrawing their support for the Bedroom Tax, 46 Lib Dem peers have voted with the Tories to keep it!
"With the Lib Dems' help, the Government defeated Labour's motion against the Bedroom Tax by just 15 votes.
"The Bedroom Tax couldn't have been introduced in the first place without Lib Dem backing. Over the past few years, Lib Dem MPs have taken the lead in defending the Tax and have voted down previous Labour attempts in the Commons to abolish it.
"Just as on tuition fees and VAT, this week's events over the Bedroom Tax show that you can't trust a word two-faced Lib Dems say.
"David Cameron and Nick Clegg's Bedroom Tax has been a disaster, neither making many more homes available to ease over-crowding, nor saving money on benefits. It's pushed hundreds of Hull families into spiralling debt through no fault of their own.
"Ministers should scrap it. If they don't, the next Labour government will."
The Bedroom Tax hits over 400,000 disabled people and 60,000 households with carers across the country. 80,000 people have been hit with the Bedroom Tax in the Yorkshire and Humber region, including 50,400 disabled people.
For the vast majority of those affected, there is nowhere smaller to move to. Last October, Hull City Council had only 25 one or two bedroom homes available - but 4,700 Hull council tenants hit by the Bedroom Tax.
This week marked the first anniversary of the introduction of the Bedroom Tax.