The change, introduced against the recommendations of the Government's statutory adviser, the Social Security Advisory Committee, has taken effect before Parliament has had a chance to debate it.
Thousands of working low-income families earning less than pounds 200 a week were told last week to return benefit books and give up hundreds of pounds.
The move was described as "extremely mean-minded and mean-spirited" by Keith Bradley, a Labour social security spokesman. Both Labour and the Liberal Democrats will vote against the change when MPs finally debate it, but by then most of the 15,000 families to be affected will have had their benefit cut.
The sudden blow to some of Britain's lowest earners, whom ministers hold up as praise-worthy examples of people who are standing on their own feet rather than forming part of the dependency culture, has happened because Peter Lilley, the Secretary of State for Social Security, has changed the rules for Family Credit.
The benefit goes to families, including lone parents, in low-paid work to supplement their wages, and is awarded for six months at a time. The average award is pounds 54 a week. Until now it has been paid in six-month blocks, even when a child leaves school during the award period.
To save just pounds 8m on the pounds 1,900m Family Credit bill, the benefit is being withdrawn on the date the child leaves school. The cash is being taken away from current claims, slashing income that families had been promised for a six-month period.
"I am just appalled," said Kate Beech, 52, a divorced single mother with two daughters, the younger of whom has just left school after finishing her A-levels. "The first I knew of this was in early June when I got a letter saying that subject to Parliamentary approval they were changing the rules.
"The next I heard was on Monday when I was told that from Tuesday I have to return my benefit book, even though my award runs through to October. That is pounds 57 a week that is just disappearing. I have budgeted for that money, and it is just being taken away at barely a month's notice. It feels as though the Government has stolen pounds 810 from me."
Mrs Beech works 22 hours a week as a library assistant in Sussex and takes home pounds 460 a month, out of which she pays pounds 350 for a privately rented home. A four-year wait for council housing has been unsuccessful.
Together with the loss of child benefit and housing benefit as her younger daughter, Gillian, formally becomes an adult, Mrs Beech calculates she will lose pounds 100 a week and will have just pounds 41 left to buy food and fuel, after council tax and other bills.
"I have worked out that I would be better off on income support," Mrs Beech said. She will, however, carry on working "because it keeps me sane although I am not at all sure how we will manage".
"I knew that from October I would lose Family Credit," Mrs Beech said. "What I cannot understand is them taking away money they have already promised. Family Credit is a big part of my budget. It is virtually my only cash in hand as all my salary goes on rent and bills. Until last month I knew where I stood until October, and now it's just gone."
Mrs Beech would like to work full time, but she says there are no full- time library jobs at present she would be reluctant to give up the security of her part-time job for a full-time job if itwas insecure.
Her anger is compounded because the Government has not called back benefit books in situations where a second child remains at school. Even though these families' benefit entitlements also fall, the Department of Social Security said the administrative cost of rewriting current order books would be too high. That, Mrs Beech said, "just makes it feel even more unfair".
A DSS spokeswoman refused to comment on the withdrawal of cash that had already been pledged, saying only that there was no provision to protect existing cases.
The change has taken effect without Parliamentary debate because Mr Lilley used secondary legislation which requires MPs to demand a vote if they oppose it. The Liberal Democrats and Labour have done that, but Parliamentary time may not be found until the autumn.
Mr Bradley said that, by withdrawing cash already awarded, Mr Lilley was effectively using "retrospective legislation" in an "extremely draconian way". Ministers were increasingly using secondary legislation to implement changes before MPs could debate them, Mr Bradley said, "undermining the whole purpose of Parliament".
That has been done with a range of recent benefit cuts, including controversial cuts to asylum seekers' benefits. In that instance, the courts eventually ordered Mr Lilley to go back and introduce primary legislation.Reuse content