The Defense Department should buy more products and services using General Services Administration contracts instead of writing its own contracts, an industry group said Thursday in a letter to Defense Secretary Robert Gates.

Larry Allen, president of the Coalition for Government Procurement, said redundant contracts used by the Defense Department are a big concern for contractors, especially those in the information technology and professional services fields.

"Our members tell us that they work with dozens of different [Defense] contracts, many of which perform the same or similar functions," Allen wrote.

That duplication increases the department's overhead costs and taxes an acquisition work force that is already stretched thin, the letter said.

Allen also criticized a Defense program that offers incentives to acquisition workers who produce new contracts. Employees should instead be rewarded for using existing contract vehicles that offer good value, he wrote.