NCP heavyweight and former Union Minister Praful Patel today criticised the Opposition parties for boycotting the GST launch function.Congress, Trinamool Congress and the Left parties have decided to boycott the GST launch in Parliament, scheduled to be held tonight."All parties unanimously passed #GST in parliament. State Governments of different parties approved the rates. Now why so much fuss over the launch function," Patel tweeted.Prime Minister Narendra Modi has also expressed their boycott launch function on Friday "unfortunate"."It was on the PM's insistence that as many as 155 letters were sent out in the signature of the minister of state for PMO Jitendra Singh on June 23, thanking all chief ministers, leaders of all recognised national and state parties as well as state chief secretaries for their cooperation in passing GST with unanimity," a government official had told ET earlier.