Congress senior spokesperson Anand Sharma demanded that BJP President Amit Shah apologise to the country for what the government had "done to Dalits".
He alleged thee was a larger agenda to weaken the security net and legal protection given to members of Scheduled Castes and Tribes under the Act.
Mr Sharma also hit out at Law Minister Ravi Shankar Prasad, accusing him of spreading lies on the issue by claiming the government was not a party to the SC/ST issue in court and demanded that he also tender an apology to the country.
The Government was a party to the case before the court, he said, displaying Supreme Court orders which showed that the additional solicitor general had appeared on behalf of the Central government during the hearing of the case.
"The Modi government is conspiring to violate the rights of Dalits and tribals by speaking lies and falsehoods. The SC/ST Atrocities Act that was brought by the Congress and Rajiv Gandhi has almost been finished at the hands of the Modi Government and its Law Ministry," Congress communications in-charge Randeep Surjewala said.
He added that while Mr Prasad claimed his government was not a party to the case in the Supreme Court, on November 20, 2017, the top court had issued a notice to the Central government along with the Maharashtra government and again on January 31, 2018, the additional solicitor general had represented the centre and sought more time from the court on behalf of the Union government.
Mr Surjewala alleged that Mr Prasad was trying to mislead the country as part of a bigger conspiracy under "an agenda of lies and falsehood".
"Was the government of India protecting the SC/ST Act or making it ineffective? The fact is that the Modi government and Law Ministry conspired to nullify the SC/ST Act under a conspiracy of lies, falsehood and deceit. And all this happened at the behest of the prime minister, the RSS and the BJP, who have an anti-Dalit and anti-tribal mindset," he said.
Mr Sharma added that Mr Shah was trying to portray himself as a champion of the philosophy of Dalit icon B R Ambedkar, but should instead apologise to the country for what "his party's government has done to the Dalits of India - for the atrocities, for the murders, for the rapes".
"The BJP and RSS's thinking militates against every aspect of the values and philosophy which Dr Ambedkar had propounded," he said.
Mr Sharma said Mr Prasad told the media on Monday the government of India was not a party to the case before the Supreme Court.
"The Law Minister has made a factually incorrect statement. He should withdraw the statement and apologise for making a wrong statement.
"It is a matter of concern that the Law Minister of India is either ignorant of the development that took place in the Supreme Court...The Law Minister was wrong in saying that the Union of India was not a party; they were very much a party," he said.
Mr Sharma said the government was represented, but they did not argue the case as it "opened the window for anticipatory bail".
"The government endorsed by default by not telling the Court that it cannot dilute the law, it cannot reinterpret the law, it cannot change the law. So, the government is a willing party to what has happened," he said.
Violent protests broke out in several states on Monday, as Dalit organisations spearheaded a Bharat Bandh, alleging that the Supreme Court had diluted the Scheduled Castes and the Scheduled Tribes (Prevention of Atrocities) Act, 1989.