Two weeks ago officials at the DWP's Child Support Agency told a committee of MPs that planned job reductions would take place despite uncertainty about whether the new systems would be successfully deployed.
Earlier this year chancellor Gordon Brown announced plans to cut 100,000 civil service jobs part of a drive for public sector efficiency.
However, the Social Services Advisory Committee in its annual report said the DWP should not assume new IT systems would allow it to cope with fewer staff.
"Although detailed plans have not yet been made public, we are concerned that the reductions are based on the presumption that IT improvements and benefits and procedures simplifications will enable the department to provide customer service continuity and improvement with many fewer members of staff," the report said.
"In our view, it would be much less risky to have any reduction in staff numbers following from a successful roll-out of new systems and processes.
"From what we have seen from our visits, there is currently little slack in the system, and a fair number of pressure points, especially within the more complex areas of benefits decision-making and assessment," it said.
The DWP has major problems with IT projects, including the Tax Credit System. In August 2003, the department estimated the level of overpayments awarded under the old tax credit schemes were between 10% and 14% by value, or £510m to £710m over the full year because of errors in the system.
The advisory board also criticised of the complexity of the social security system and the IT used to support it.
"The complexity is both driven by, and drives, the IT problems that the department faces. While there have been improvements during the last decade, the department probably remains as far behind the outside world in its systems as it ever was," the report said.