Karen Matthews was convicted last week of kidnapping her daughter. The case is important, not because of what she did, horrible though that was, but what she has exposed. She opened our eyes to an underclass that most of us ignored or hoped would just go away.

Matthews is the mother of seven children by five different men. She has never worked, but lived off benefits of £286.60 a week. The Matthews’s house was filthy. A neighbour declared, “I wouldn’t want to keep a pet dog in there, let alone children.” Her relationships with men were so promiscuous that when police built up a family tree it stretched to 300 names.

Karen’s nine-year-old daughter Shannon was regularly drugged to keep her quiet, had feet encrusted with dirt, was infested with head lice and flinched at any sudden noise. Police found a note scribbled by Shannon to her brother: “Do you think we will get any tea tonight? If we’re quiet we might get a bag of sweets. Don’t talk too loud or get a beating.” This was in a family receiving in benefits the equivalent of £20,000 a year before tax. Seven children were going hungry to bed, not because of social deprivation but because their mother could not be bothered to feed them.

The Matthews household is not a one-off. Researching a report on the care system, I met many children from families such as the Matthewses – including teenagers so starved and abused that it had stunted their growth. One boy recalled taking speed each morning “just to get me to school”. Another had been given nothing to eat but dry cornflakes for three days. A third was told by her mother on her 13th birthday, “Go out and sell your body. I am not feeding you any more.”

Who is to blame for the suffering of these children? Like Shannon, the great majority had been neglected and abused by their mothers. Politicians point to the breakdown of the family and the absence of fathers, but this is a fundamental mistake. They are presuming there is a family in the first place to break down.

A drug dealer from Brixton, south London, and father of five children by three different women described what would happen. He would start seeing a woman. Two weeks in and “bang, she gets pregnant”. There is no discussion about it. As far as he is concerned they are barely an item, let alone a family. They are certainly not living together.

He laid the blame squarely on benefits: “Women get money from the government. Men get eradicated. What do you need a man for? The government has taken our place. I am old-fashioned, from the ghetto, and I am serious for my kids. But the government is the provider now. You see your child suffer and it mashes you up.”

The figures bear him out. Single motherhood is obviously an attractive proposition. Britain has the highest rate of teenage pregnancy in Europe and, in 2001, 90% of births to mothers under 20 occurred outside marriages. Two young men from council estates as far apart as Hastings and Newcastle insisted that girls giving birth at 16 or 17 were no longer the exception in their area but the norm.

To accuse these young girls of being feckless is unjust. They understand and are responding to the economics of the situation.

They have grasped better than most politicians the consequences of our poor education system. Last year fewer than half of teenagers finished compulsory schooling with five good GCSEs including maths and English. Recently Ofsted declared that almost 1.5m pupils attend secondary schools with substandard teaching and discipline. Christine Gilbert, head of the school standards watchdog, pointed out in her annual report that it is the poorest children who are most likely to get a raw deal from the system.

What future is there for a girl who graduates from one of these schools? Skilled and hard-working eastern Europeans monopolise menial jobs. The next step up – a job in, for example, catering or hairdressing if she can get it – pays about £10,000 a year before tax. This is slightly less than a single mother with two children receives in benefits and does not include somewhere to live rent-free.

Sir Norman Bettison, chief constable of West Yorkshire police, the force responsible for bringing Karen Matthews to justice, put it starkly: “We are talking here about the perverting influence of welfare. The more kids you have, the more money you get.” For some it is the only option.

Many single mothers are excellent parents. I am a single mother myself. But the situation created by the government is on a different level altogether. It has put young girls in a position where the only career open to them, the only possibility of an independent life, is to have children – whether they want to or not.

The consequence for the teenage mothers, their children and society is immense. Mothers of children on the “at risk” register are five times more likely to be teenage mothers, according to Jill Kirby, author of an excellent report, Broken Hearts (published by the Centre for Policy Studies).

Babies born to teenage mothers are 60% more likely to die in their first year than those born to other parents. A report from the Children’s Society claims that 25% of all youngsters living in step-families run away before the age of 16; many are younger than 11. The Joseph Rowntree Foundation, a social research charity, discovered that children with one parent are more likely to have behavioural problems, do less well at school, have sex earlier, suffer depression and turn to drugs and heavy drinking. They are also, according to evidence from the States, more likely to get involved with gangs and crime.

The government has recognised this with a plethora of schemes to intervene ever earlier in the life of the disadvantaged child. So far it has concentrated on the consequences of single parenthood, but not the cause. This is self-defeating.

What is the point of setting targets to end child poverty when its policies are creating tomorrow’s poorest children – and grandchildren? Karen Matthews was herself one of seven children in and out of care.

A young man from a Midlands estate said to me with a sigh during the course of my research: “The authorities do not know what to do with us. They can only keep us out of sight and mind.”

The kidnap of Shannon Matthews might finally force this issue into the open.

Minette Marrin is away

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