In an interview with the English news channel Times Now, the prime minister said opposition parties supported the tax reform in the parliament, but outside they sang a different tune.
"Once the meeting is over, they come out and show anger," he said.
"The chief ministers of the opposition parties have also participated in the decision-making process of the GST. The decisions are taken by consensus, according to a system created by the parliament and the political parties themselves," he said.
The GST an indirect tax levied in India on the sale of goods and services came into effect from July 1, 2017.
The tax replaced existing multiple cascading taxes levied by the central and state governments. (ANI)