His comments came as the agency, which is responsible for assessing and collecting child maintenance, took on its first cases. Until now, payments have been set by the courts under a system that has been condemned as inconsistent and unfair. Less than 30 per cent of single mothers receive any maintenance from ex-partners.
Under the agency, 800,000 lone parents would receive financial support, twice as many as at present, Mr Lilley said. The Government hopes that this will save pounds 600m a year on its social security budget.
Ministers argue that regular maintenance will encourage unemployed single mothers who want to return to work. Unlike income support, which is withdrawn when women obtain employment, maintenance payments can be retained.
However, neither Mr Lilley nor Ros Hepplewhite, the agency's chief executive, were able to say how many women would be better off. Lawyers say most will not benefit at all because their income support will decrease as maintenance payments rise.
After the press conference, the agency released figures showing that 22,000 women refused to name the father of their children when interviewed by social security staff last year. Under the Child Support Act, women can be penalised if they refuse to identify their ex-partners without good reason.