The Congress reaction came after President Ram Nath Kovind signed an ordinance on Thursday for amendment to the Code, which was sent to him by the Union Cabinet a day earlier.
"It is an example of a hurried legislation. The Act has a lot of potential but many gaps have been left because of the hurry to declare it exactly as the Goods and Services Tax.
He said he would reserve comments till he saw the final version. "If it is properly plugged, I would support it."
He urged the government to seriously consider and try and plug as many loopholes as can be through the amendment.