Try as I might – and I did – I just couldn't find out how many bedrooms there are at Chequers, stately weekend pile of serving Prime Ministers.

But since it self-describes as a country mansion and is set in a 1000 acre estate, we can safely assume Dave need never worry where to stash Sam Cam's mam when she pops in for a sleepover. Even with a couple of dozen of her chums.

It's safe to assume too that multi-millionaires with at least a couple of private homes to hand – step forward most of the current Cabinet – need never worry their pretty little heads about bedroom numbers given that they're not about to need housing benefit for a socially rented pad any time soon.

So perhaps there's a tiny failure of imagination here in visualising how most of the rest of the planet live. Most especially those about to fall victim to the so-called bedroom tax, surely the nastiest government gambit since the imposition of a tax on windows in 18th century Scotland. (And almost 100 years later in England, as is the way of these tax experiments.)

In essence, it means a household with two working adults is deemed to need not more than one bedroom. With two kids of the same sex under 16 thrown in they can have just one more. Ditto with two kids of different sexes under 10. Any more and you lose housing benefit on a sliding scale. For the 95,000 Scots affected, the losses will be in the range of £10 to £22 a week.

For people already earning little enough to qualify for housing benefit, that is a huge dent in the weekly budget. The Convention of Scottish Local Authorities (Cosla) reckons that a fifth of Scotland's council house tenants will be hit and 40% of those will swiftly rack up rent arrears.

People 250 years ago got round their daylight being taxed by bricking up windows – bad for the soul, but cheaper on the wallet. Avoiding paying this extraordinarily mean-spirited tax on a "spare" bedroom is going to prove trickier.

As Saturday's Herald reported, some legal advice suggests that a room not tricked out like a conventional bedroom might be deemed exempt. But I suspect those lovely people at the Department of Work and Pensions are unlikely to endorse that lifeline any time soon.

They've already indicated they will use housing landlords' definitions rather than current living arrangements. That sounds to me to mean if you're renting a notionally two-bedroomed house, the benefit will be calculated on that basis regardless of current usage.

This bluntest of instruments takes no account of people's individual needs or lifestyles.

No account of a family where illness or disability means the adults require separate sleeping arrangements. No account of why a special needs child might need separate space for therapeutic equipment or a visiting carer. Imagine the stress this appalling initiative will add for people already dealing with more than their share of anxieties. And no account of the normal, civilised way folks aspire to lead their lives ... being able to have friends or relatives sleep over. Or the tens of thousands of children who divide their week between separated or divorced parents.

Even people who keep space for foster children will lose out. Is the world suddenly so over-provided with foster carers that it can afford to exclude anyone on housing benefit?

The party line, if one can still use that term about an increasingly fractious Coalition, is that the vulnerable will be protected. But the £30m set aside for that purpose is a fleabite in a pan-UK context.

And here's another thing. The Prime Minister said last week that he didn't see why people in publicly rented properties should pay less for extra rooms than those in the private variety.

There are at least two things wildly amiss with that statement. The first is that one of the main reasons for the housing benefit cost explosion is rapacious private landlords. Nobody seems keen to take a similarly blunt instrument to their naked exploitation of families desperate for a roof anywhere near their working postcode.

And the second is born of sheer ignorance of the national housing estate. Those people willing to sign up for downsizing should not hold their breath for finding a smaller property. One-bedroomed homes are like hen's teeth in many areas. Greenwich in London did a survey and found 15 such properties vacant to service a waiting list of 800.

So what can be done to alleviate onrushing misery and debt? Mike Dailly's Govan Law Centre in partnership with Shelter, Money Advice Scotland, Citizens Advice and Oxfam have launched a petition on the Scottish Government website which asks that the Housing Scotland Act be amended so that debts incurred through housing benefit cuts can't be used to evict people from their homes.

Some English regions like Merseyside and the West Midlands have merged the housing estates of housing associations and local authorities to create a larger pool from which people can try to access the size of home they need or can afford.

And March 30 will see major public protests in Glasgow and Edinburgh.

But if you're in the mood for irony consider this. Last week 11 European countries including France, Germany, Spain and Italy – the largest economies – agreed to implement the Tobin tax. Just 0.1% levied on traders of stocks, bonds and derivatives – some of the chaps whose roulette games prompted the crash.

It will fetch them a cool £30bn. If the UK Government had agreed to join them, it could have netted £8bn.

But why take pennies from the rich, when you can properly screw the poor?