12 legislators are in Mumbai since Saturday after resigning from the Karnataka Assembly.
The Congress in Maharashtra accused the BJP of attempting to destablise the democratically-elected government in Karnataka, where over a dozen legislators of the ruling combine have resigned.
Maharashtra Congress president Ashok Chavan said what was happening in the southern state was detrimental for democracy in the country.
Another party leader Satyajit Tambe said the Mumbai police were planning to send Karnataka minister DK Shivakumar, who is in the city to meet rebels legislators, back to Bengaluru.
Twelve legislators -- seven of the Congress, three of the JD(S) and two Independents -- are in Mumbai since Saturday after resigning from the Karnataka Assembly and withdrawing support to the coalition government. They are staying in a luxury hotel in suburban Mumbai.
Two more Congress legislators tendered their resignation today to the Assembly Speaker.
Mr Chavan accused Maharashtra Chief Minister Devendra Fadnavis of encouraging efforts to destablise the 13-month-old Congress-JD(S) alliance government.
The rebel legislators of the ruling combine have been held captive in Mumbai under police watch, he alleged. "The BJP earlier made a mockery of democracy in Goa and Manipur," the former Chief Minister alleged. "(Most of) the rebels are Congress legislators, but party leaders are not being allowed to meet them. This is suppression," Mr Chavan said.
"BJP was strangulating democracy. The way DK Shivakumar was taken away while taking to reporters was condemnable," Mr Chavan tweeted.
He also condemned the police action against Shivakumar and Maharashtra Congress leaders Milind Deora and Naseem Khan. Mr Shivakumar, Mr Deora and Mr Khan were detained from outside the hotel by the police and taken to a guest house in the Mumbai university campus in suburban Kalina.
Meanwhile, Maharashtra Youth Congress president Satyajit Tambe claimed the Mumbai police are planning to send back Shivkumar to Bengaluru.
Mr Tambe said: "The Mumbai police are planning to deport Shivkumar by a plane to Bengaluru. Despite several requests, the police have not
allowed us to meet him. Some Congress workers were also manhandled outside the guest house."
Mumbai Congress leader Sanjay Nirupam also said he was not allowed to go inside the guest house, where there is a massive deployment of police. The BJP has denied any role in the resignation of Karnataka ruling alliance MLAs.
The BJP has demanded the resignation of Karnataka Chief Minister HD Kumaraswamy, who they claim, has lost majority in the House after the resignation of 14 legislators.