Sources said the Congress at today's meeting of the Select Committee pushed for a "pure GST" with states not being given powers to impose one per cent additional tax over and above the GST rate.
The main Opposition party got "some support" on its stand about the role of states in the GST Council and the compensation to them, sources added.
Another proposal supported by "some members" was to replace the word "may" with "shall" with regard to the payment of compensation that the Centre can give to states for loss of revenue on introduction of the single-rate Goods and Service Tax regime, sources said.
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The Congress, sources said, may give a dissenting note on the additional tax as well as keeping petroleum products out of the GST regime in the present Bill.
The Committee, which is vetting the constitutional amendment Bill, will meet again on July 17 and 20, by when a draft could be ready.
The panel, headed by Bhupender Yadav, has so far not decided when it will present the report to the Rajya Sabha, which opens on July 21 for the monsoon session, sources said.
As per the GST structure, 100 per cent compensation would be provided by the Centre to states for first three years, 75 per cent for fourth year and 50 per cent for the fifth year.
In order to address concerns of the manufacturing states, the GST Constitutional Amendment Bill has provided for an additional one per cent tax for a period of two years.
The government is racing against time to meet the April 2016 deadline to roll out GST.