It has emerged the Child Support Agency's troubled £1.1bn computer system has needed 130 changes in eight years to get it working properly.
The agency's CS2 computer system, which was built by EDS, has been plagued with technical problems since it was launched in 2003 and the government is not expecting to finish inputting all child-maintenance claim cases until 2013.
Now work and pensions minister James Plaskitt has admitted to Parliament that the CSA has requested 130 detailed changes to the specification for the CS2 IT system since 2000.
The revelation about the number of tweaks needed to get the system running properly has prompted accusations of a "fundamental" problem in the system's design process, and that part of the blame for its poor performance lies with the government.
Richard Steel, vice president of local government IT user group Socitm, said: "When designing a complex IT system, a prerequisite is fundamental review of the relevant businesses processes before the detailed specification can be produced. A high number of changes may be an indication that this did not take place, and that the customer is attempting to skew the system design to suit the ways in which they are used to working."
Socitm development services manager Dilip Chudgar added: "A high number of complex changes certainly suggests something has gone fundamentally wrong in the process design."
For years, bugs in CS2 have prevented the transfer of cases from the old system and thousands of cases required manual intervention to unlock them after becoming "stuck".
Delays in processing claims meant in 2006 there was still £3.5bn of outstanding maintenance payments to be collected, with only one in three parents receiving any payment.
The CSA was branded one of the "worst public administration scandals in modern times" by MPs in 2006 and was axed following a review by Sir David Henshaw.