Brookly McLaughlin, a Treasury Department spokeswoman, said the agency had no comment on Davis' letter or on the status of the telecommunications deal.

Davis argues that participation in Networx is a better strategy because the government can save money, streamline the number of vendors used, improve security and interoperability and avoid a duplication of efforts by staying with one major contract.

In his letter to Evans, Davis assailed the Treasury Department's solo efforts to sign a deal, saying the agency "did not have an adequate business case for moving forward with TCE and has performed no coherent cost analysis comparing TCE with GSA telecommunications vehicles." The GAO's report last year was also critical of the agency's direction on TCE, he said. The report stated that "it is difficult -- based on the extent and quality of the documentation provided -- to understand why Treasury still intends to proceed with TCE."

"Notwithstanding these difficulties, Treasury has insisted on plowing forward with the acquisition yet another time," he wrote in his letter.

Davis pointed out that Homeland Security, which has more complex telecommunications needs than the Treasury Department because of its mission, has agreed to use Networx for its ongoing communications systems. Davis said the DHS decision to use Networx essentially negates the Treasury argument that its needs are too complex and diverse for it to join Networx.