Up to 50,000 unmarried mothers face losing their benefits in the Government's latest crackdown on social-security fraud.
Peter Lilley, the Secretary of State for Social Security, is expected to announce new measures tomorrow to try to cut pounds 100m-a-year fraud from the Child Support Agency.
The news comes as a report says some mothers have been put under "considerable pressure" to co-operate with the agency despite evidence that their former partners were violent. The study, by the Joseph Rowntree Foundation, published on the third anniversary of the Child Support Act, also says poorer families have lost out under the radical reforms of the CSA and that working mothers claiming Family Credit have been unable to rely on maintenance being paid regularly to them by the CSA.
Mr Lilley's proposals are aimed at mothers who claim benefits while secretly getting help from ex-husbands and boyfriends. It will be disclosed in a report to be sent to the all-party Commons Social Security Select Committee this week.
Last year Frank Field, chairman of the committee, told the Commons the agency knew of at least 16,000 cases where divorced or separated parents were colluding "to defraud the taxpayer".
At present women are allowed to withhold the father's name if they have a good reason or it would cause "harm or undue distress".
By alleging she is in danger of being beaten up or threatened by her ex-partner, a mother on benefit can stop maintenance being enforced through the CSA.
Subject to an interview, she can continue to receive full benefit and the absent father pays nothing - or at least nothing through the agency.
A spokeswoman for the CSA said that when women refused to name the father "we have to take each case on individual merit. Our officers have to be very careful and look at all different factors before making a decision".
At present those who do not co-operate with the CSA face having their benefit cut by 20 per cent for six months and then 10 per cent for a further 12 months.
But Mr Lilley wants an immediate 40-per-cent reduction on lone parent benefits of pounds 46.50 a week if the mother fails to co-operate with the CSA. He is said to be considering stopping the benefit altogether but this would need new legislation.
Benefits paid for each child - pounds 15.95 a week for under 11 and pounds 23.40 for those aged 11 to 15 - would not be affected.
But the Rowntree report said that some mothers who had asked to be exempted from providing information about the fathers of their children on the grounds of "harm or undue distress" had come under considerable pressure to co-operate despite evidence that their former partners were violent.
Karin Pappenheim, director of the National Council for One Parent Families said: "It is extremely important that the provisions to protect vulnerable lone mothers and children are maintained for the many mothers who have very genuine reasons not to involve the father. That protection has been working well.
It is essential fraud is tackled but it would be a tragedy if that is achieved through measures that may jeopardise the safety of women and children who are genuinely at risk."Reuse content