The Hyderabad-based Majlis-e-Ittehadul Muslimeen (MIM) withdrew its support for the Congress governments in both Andhra Pradesh and the Centre on Monday.
The MIM president and the party's lone member of Parliament, Asaduddin Owaisi, accused the Kiran Kumar-led Andhra government of giving a free run to the Sangh Parivar.
"We are ready to face the political consequences of this decision," he said.
Sources said many senior Congress leaders are trying to persuade Owaisi to reconsider the decision.
RJD leader Lalu Prasad and West Bengal CM Mamata Banerjee were among the non-Congress leaders who spoke to Owaisi. The Congress, however, claimed that the UPA had "got the numbers it required".
With the 19-member TMC and two-member Jharkhand Vikas Morcha-Prajatantrik having already withdrawn their support, the number of Congress-led coalition MPs in the lower house has now been reduced to 254.