Lone parents, the main target of Labour's "welfare to work" campaign, now have less work than ever as double-earner families mop up the spare employment, according to a Government-sponsored report.
Single mothers grew even poorer in the past decade as jobs were taken up by two-parent households, says the study, carried out by researchers from London University's Institute of Education and the Thomas Coram Research Unit.
Double-income families could be making the problem even worse by re-generating a servant class, says the report, because working parents have no time to look after their own children. They could also be driving up the cost of childcare, putting it beyond the reach of poorer families.
Children's welfare experts believe the findings increase the pressure on the Government to produce hard-nosed changes to the benefits system that will help single parents.
While lone parents have suffered, employment among mothers as a whole actually increased between 1984 and 1994 - and especially among women who have very young children, under the age of five.
But the researchers say this growth in work is overwhelmingly among well-educated women who already have a partner in employment.
One result is a further decline in the traditional family unit where the father goes to work and the mother stays in the kitchen. At the same time there has been a growth in the number of single-parent families.
"There has been an increase both in the proportion of 'work poor' families (with no earners) and in the proportion of 'work rich' families (with two earners)," says the report.
"There is a growing number of continuously employed women who live with partners. Both parents in these households not only work, but work full time and often for long hours. They constitute a growing cadre of high-status, high-qualified and high-income families.
"At the other end of the household spectrum, there is a growing proportion of 'work poor' families, mostly headed by single mothers who are not employed, are dependent on state benefits and bring up their children on low incomes.
Around one-third of children are thought to live in households with no full-time earners.
John Rae Price, director of the National Children's Bureau, called for wholesale changes to the benefits system so that single mothers were rewarded for choosing to work. "So much of the current lack of confidence in parenting is associated with the lack of economic self-respect and independence," he said.
Mothers, Fathers and Employment - parents and the labour market in Britain 1984-1994 is available from the social analysis and research division of the Department for Education and Employment (tel: 0171 925 5000), price Pounds 4.95