I have to say that the Bedroom Tax is a bad thing - a bad, iniquitous, social engineering abomination of a thing - but also that it is misrepresented in many ways.
Firstly as being a LiberaTory coalition measure. The phase of the bedroom tax being rolled out to all social housing tenants didn't happen til after the 2010 election, but even that had been announced back in 2008.
The earlier phase - which, like the one attracting faux outrage from Labour and their fellow travellers, was also a Labour initiative - was when it was rolled out in the private sector. As "Local Housing Allowance" it had a different branding and slightly different structure, but that's a factor of the different way that rent levels are negotiated in the private and social sector: Housing Association tenants can't haggle a couple of quid either way in their rent as it gets set at a given rate for a type of propert right across the whole of a given social landlord.
So I'd grant you that it was a "coalition measure", but a Co-Op/Labour coalition one, not a LiberaTory coalition policy. Brown's majority was thin enough that it couldn't have happened without the Co-Operative Party lending Labour enough votes to get it into law: if you ever hear a Co-Operative MP rail against the bedroom tax, ask what they got in exchange for enabling it.
The cacophony of opposition to the 2010 phase compared to the silence in 2008 is notable. In part that is about how Labour's front organisations toe the party line, in part a reflection of how the social sector has as landlords funded organisations with staff and resources that can give a unified, co-ordinated voice, whereas hundreds of thousands of individual private tenants lack an equivalent. Our lackadaisical press leave awkward facts like this unmentioned.
But even before 2008 the first phase, perhaps we should call it phase zero, was the trialling of the basic idea. That's from back when Gordon Brown was at the Treasury rather than in Number Ten, indeed it's even older than I thought it was. Some googling and I can trace it back to a remark from Malcolm Wicks, Secretary of State for Work and Pensions, back on 19th December 2001, who explained in the House, "the under-occupation pilot encourages housing benefit recipients living in under-occupied social housing to move to smaller and cheaper accommodation in order to make more efficient use of housing stock".
That was about a successful pilot of the bedoom tax, so it must have started either just after the second 90s/00s Labour landslide or possibly even during the generally-not-that-bad 1997 government, which I tend to consider the second least bad government I've lived under. And just think: 2001, you could have had nine years of housebuilding to tackle the housing benefit bubble by 2010 if you'd wanted, and let supply and demand fix things.
Just when you think Labour are a bunch of Tories, they turn out to be a bunch of brazen spin-doctoring Tories instead.