The planned overhaul of the Child Support Agency was postponed last night because of problems with the new computers that will handle claims.
The switch to a new, streamlined system of payments to lone parents was delayed just one month before the reform was to be launched.
In a Commons statement, Alistair Darling, the Secretary of State for Work and Pensions, said extra time was needed to test the CSA's new multimillion-pound computer network.
"The delay is frustrating and is regrettable," he said. "There was a choice. I could have taken a chance, but that meant taking a chance on support for children and for parents. That could not be justifited." He added: "I know many parents are anxious to see the changes introduced as soon as possible, but I judged the risk of proceeding before testing was complete was unacceptable."
The CSA computer system, which was due to come on stream on 22 April, is being developed by the American company EDS. Its introduction had already been delayed from last October.
The system will initially handle new CSA claims, while the 1.06 million existing cases will be transferred once the new computers have bedded down. Under the Government's reforms, the complicated formula for payments will be swept away and replaced with a simpler system.
The Work and Pensions Department was unable to confirm last night when the CSA computers would be ready to process fresh claims, but said the firm would not be paid until they were up and running.
The Liberal Democrat MP Steve Webb described the delay as a "shambles". He said: "If this computer system can't cope with the trickle of new cases, then what chance is there that it will be able to handle the flood of existing cases once they are transferred? It is the latest in a long line of botched government IT projects."
Kate Green, director of the National Council for One Parent Families, said: "The delay is disappointing but the system has to be right so that children get a properly resourced service that actually delivers the maintenance they need, rather than a rushed, untested system which parents could have little confidence in."Reuse content