He also held that the Central Board of Excise and Customs (CBEC) can perform the same work at much less expense.
Swamy, who has been critical of the firm set up by the UPA government to provide support structure for GST rollout, in his latest letter said the Cabinet should examine the matter fully before taking a final decision.
"The Cabinet may perhaps therefore have the matter fully examined before a final decision is taken in the matter," Swamy said.
The Goods and Services Tax Network (GSTN) is the special purpose vehicle that was formed under the previous UPA government to set up the information technology framework for rolling out the indirect tax regime that will replace a string of local levies.
In the letter, Swamy drew attention of the Prime Minister towards his earlier letters in which he had said it was "not in our national interest" to pursue GSTN within the present structure as it involves majority participation by the private sector whose shares are largely foreign owned.
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