Banerjee, stung by defections herself with several of the Trinamool Congress MPs and MLAs joining the BJP, dialled the Karnataka chief minister last evening and spoke to him over the political crisis in the state, the sources said.

They said it was during this conversation that Banerjee suggested about the protest by opposition parties in Parliament on Thursday. It was decided that the protest should be led by some other party than the Congress as the grand old party, which is itself embroiled in a leadership crisis, may fail to unite the opposition.

TMC lawmakers then started calling up leaders of other opposition parties, they added.

"She (Mamata) called up Kumaraswamy around 6.30 pm and discussed the situation in the state. It was then that a plan was drawn to hold a joint protest in Parliament premises on Thursday over the issue," a source said.

The Congress-JD(S) government in Karnataka is in a turmoil after several MLAs, mostly of the Congress, resigned, threatening the stability of the ruling dispensation.

The Bharatiya Janata Party (BJP) has claimed that the state government has been reduced to a minority and demanded Kumaraswamy's resignation.

MPs from the Congress, Trinamool Congress, Samajwadi Party, Nationalist Congress Party, Rashtriya Janata Dal and Communist Party of India (CPI) protested and said that the political crisis in both Karnataka and Goa was a threat to democracy.

A number of top Congress leaders, including Sonia Gandhi and Rahul Gandhi, protested near the Gandhi statue in the Parliament complex. They shouted slogans, carrying placards with messages like "save democracy" and "stop bulldozing state governments".

In Goa, the Congress suffered a major setback on Wednesday as 10 of its 15 MLAs quit the party and joined the BJP.

The Congress leadership has blamed the BJP for the desertions from its ranks in both the states.