Seven out of ten of the families are financially dependent on Income Support, compared with just over a third dependent on welfare benefits in the early 1970s.
As a result, social policy changes will be needed to increase benefits and incomes to keep one- parent families above the 'poverty plateau', according to a report by the Family Policy Studies Centre.
The study, by Louie Burghes, highlights the increase in family and child poverty. And it describes some of the disincentives facing lone parents who want to leave Income Support by working full-time, but find themselves on a 'poverty plateau' where earnings of up to pounds 170 a week leave them little better off.
Funded by the Joseph Rowntree Foundation, One Parent Families: Policy Options for the 1990s, hopes to influence the future of the welfare state, under review by the Government and Labour's Commission on Social Justice.
It warns that the cost to taxpayers of supporting one-parent families is likely to increase. Ms Burghes, a social studies researcher, says: 'The first object of new policies to improve the well-being of one-parent families must be to improve their financial situation. For many - especially those with school-age children - this is likely to be achieved by removing barriers that make it difficult or financially unadvantageous for them to work.'
The research identifies three different types of one-parent family: single, never-married parents; divorced or separated parents; and lone fathers. Divorce is listed as the biggest cause of the increase in single-parent families.
One in ten one-parent families are fathers, who are more likely to be in work than lone mothers; more than half the lone mothers are separated or divorced. The fastest growing group is single, never-married mothers whose average age is 24 and who account for three in ten of all lone parents.
One Parent Families: Policy Options for the 1990s; Joseph Rowntree Foundation; pounds 7.50.Reuse content