The really frightening thing about today's cuts is that no one knows their combined impact

The sums just don't add up.

Photograph: Getty Images

"How will I cope with the bedroom tax? I already have more outgoings than ingoings. I don't have my heating on, I don't have my fridge on. I buy reduced food, 10p loaves of bread. I go to the swimming pool to shower so I save gas. I can't make any more savings."

This is Debbie, 45, from Newcastle.

Until a few months ago, she claimed no benefits and was paying her own rent. Then she suffered a serious illness and lost her job as a support worker. She is thankful her £71 rent is currently being covered by housing benefit, but is struggling to survive on just £71 a week Employment Support Allowance. As of this month, she will be hit not only by the bedroom tax, but will also face a £64 council tax bill as Council Tax Benefit is withdrawn.

Crisis is working with Debbie to help her rebuild her life, but our fear is that these measures could leave her, and thousands of others like her, in serious trouble.

Debbie faces losing her home, and with a severe lack of one-bedroom properties in the area, she is justifiably scared about the future. She is one of millions struggling with a bewildering array of cuts that come in April 2013. The one thing they have in common is that they all hit those with least to lose - those already closest to homelessness.

The really frightening thing about today's cuts is that no one knows their combined impact. Indeed, the influential Public Accounts Committee has expressed concern that:

"The Department is introducing these significant changes without comprehensive modelling of the likely outcome on individuals"

The scale is enormous: 660,000 households will be hit by the bedroom tax; 2.4 million households by the Council Tax Benefit cut; 56,000 households by the overall benefit cap; 9.6 million households by 2015/16 by benefits uprating; 1.36 million households by Local Housing Allowance cuts; 500,000 disabled people will lose out when DLA becomes PIP. Last year 1.7 million grants and crisis loans were made to people on the brink of destitution or rebuilding their lives following homelessness - these are to be abolished, cut and localised. Even Legal Aid for housing and benefit disputes is to be stopped, so people who believe they have been treated unfairly will have no power to challenge.

The result for households budgeting for these multiple cuts will be a cold, bleak April of misery, debt, food banks, unheated rooms, unpaid rent and homelessness. Leaving aside the moral repugnance of forcing the poorest in our society to bear such a burden, this is going to cost us all dearly.

The price to the public purse of keeping someone in their home pales into insignificance next to the cost once they lose it. The price of B&Bs, hostel rooms, A&E departments, mental ill-health and rough sleeping services is enormous. These cuts are not only cruel - they are counter-productive for us all.

And they come at the worst possible time. Homelessness is already rising as the economic downturn and previous cuts take their toll. Over the past two years rough sleeping has risen by 31 per cent, and the number of households accepted as homeless by local authorities has gone up by 26 per cent. Unemployment and underemployment remain stubbornly high.

In the words of Debbie: "It will be impossible to cope - the sums just don't add up." I couldn't put it better myself. The sums don't add up for Debbie, and they don't add up for society either.