Hopes were raised that the long-delayed legislation would see the light of day this year after PM Modi invited Congress president Sonia Gandhi for tea and talks late last month. (File photo)

The Congress on Tuesday declared war on the BJP-led government over the National Herald case against party leaders Sonia and Rahul Gandhi, casting a shadow of uncertainty over the key reform, the Goods and Services Tax or GST.Furious lawmakers of the main opposition party forced repeated adjournments in both houses on Tuesday, not allowing Parliament to function at all as they raised slogans alleging a "political vendetta" against the Gandhis, who have been asked to appear before a trial court.The case has been filed by BJP leader Subramanian Swamy, who alleges that Congress president Sonia Gandhi and her son and deputy Rahul Gandhi face allegations that they illegally acquired property worth Rs 5,000 crore belonging to the National Herald newspaper "The GST Bill has gone for a sky walk," Anand Sharma, the Congress' deputy leader in the Rajya Sabha was quoted by news agency Reuters as saying. Sources close to the Congress leader later said his comment was made in jest and a final decision on supporting the GST bill would be taken by the party's top leadership. No political vendetta. A private complaint was lodged . The government had nothing to do with it. The High Court has dismissed their case and asked them to go and face trial. Nobody in this country has immunity from law," said Finance Minister Arun Jaitley, after Rahul Gandhi said he "absolutely saw political vendetta" in the case.The winter session is seen as the government's last real chance to push the GST bill through Parliament in time to meet a deadline to implement it by April 1, 2016. The government is in a minority in the Rajya Sabha and needs the support of the Congress to get the constitutional amendment through it. Prime Minister Narendra Modi had invited Sonia Gandhi for tea and talks late last month and there were consultations between the Congress and the government over the weekend on the bill, with Mr Jaitley taking time off from celebrations for his daughter's wedding, to meet Anand Sharma at his residence to discuss the GST bill.Amid the protests today, top Congress sources indicated that they would discuss proposals made by the government to address their concerns and called it "work in progress" saying the party was likely to take some time before it made a final political decision on supporting the bill in this session.