New Delhi | In a fresh jolt to the beleaguered Trinamool Congress chief Mamata Banerjee, one of her closest political aides Sudip Bandyopadhyay on Saturday joined the rebel camp that is preparing to approach Lok Sabha Speaker Om Birla on Monday to seek recognition as the "real TMC" parliamentary group.

Bandyopadhyay, a veteran parliamentarian who has long been regarded as one of Banerjee's trusted lieutenants in Parliament, met Union Minister Bhupender Yadav along with rebel TMC MP Satabdi Roy, as the dissident faction stepped up its challenge to the party leadership. He also met Union Home Minister Amit Shah.

The spree of desertion continued with former minister in the erstwhile Mamata Banerjee government in West Bengal, Manas Bhunia, also resigning from the Trinamool Congress on Saturday.

The developments came amid a deepening crisis within the Mamata Banerjee-led party, with rebel MP Jagadish Chandra Barma Basunia claiming on Friday that 19 Lok Sabha members are backing the dissident camp. With Bandyopadhyay joining the group, the number of MPs in the rebel camp is now 20.

The party has 28 members in the Lok Sabha, and 13 in the Rajya Sabha, of whom three have resigned so far.

Sources in the dissident camp said they want Bandyopadhyay to lead the group in the Lok Sabha.

The rebels have announced that they will meet Birla on Monday and seek recognition as the "real TMC" parliamentary group.

"We have submitted the letter... On Monday, we will go to the Speaker and stake our claim to form the real TMC parliamentary group. We will ask the Speaker to give recognition to our claim," Basunia told PTI Videos on Friday.

The rebel MPs are also likely to meet West Bengal Chief Minister Suvendu Adhikari on Sunday.

The TMC has been rocked by a rebellion by a large section of its lawmakers in the state and at the Centre following its defeat in the West Bengal Assembly elections.

Veteran TMC parliamentarian Saugata Roy meanwhile said he was "deeply hurt" by Bandyopadhyay's move, while Kalyan Banerjee was dismissive of it.

"What can I do? I had spoken to Sudip Bandyopadhyay three or four days ago. He told me that he was not going anywhere. He said if he did anything, we would do it together.

"But then he went to the residence of Yadav, who is the in-charge of Operation Lotus (purported political moves to split the TMC) in West Bengal. The interpretation for this is anybody's guess," Roy said.

Kalyan Banerjee meanwhile said it's not a "big deal". "Let it be. Many people have left, Sudip da has left too. What's the big deal? Nothing," he said.

Rejecting the dissidents' claim, former TMC Rajya Sabha MP Saket Gokhale said MPs seeking recognition as a separate parliamentary group would face disqualification if they backed the BJP-led NDA.

Claiming that the anti-defection law offers no protection for a "split", Gokhale said the Constitution's 91st Amendment had removed provisions relating to splits and argued that forming a separate parliamentary group enjoyed "zero protection under law".

Rejecting suggestions that the dissident MPs could merge with the BJP, Gokhale said a merger required the entire political party and not merely its parliamentary wing to merge.

"The 'split' attempt is dead," he said, adding that backing the NDA or defying the party whip would amount to defection and attract disqualification proceedings.

In the Rajya Sabha, three TMC parliamentarians -- Sukhendu Sekhar Ray, Sushmita Dev and Prakash Chik Baraik -- have resigned from both the party and the Upper House this week.

Amid the turmoil, TMC National Joint Secretary Derek O'Brien on Saturday dismissed speculation about the party merging with another political formation, terming such reports "fake news".

"Let me put an end to this fake news about the AITC merging with any other party. Baseless. Yes, that's the perfect word used by my friend KC Venugopal," O'Brien told PTI.

Rumours of a possible merger had gathered pace after a series of meetings involving senior TMC and Congress leaders in New Delhi this week, including between Mamata Banerjee and Sonia Gandhi, and between Abhishek Banerjee and Rahul Gandhi.

Both the Congress and the TMC have dismissed speculation about a merger, maintaining that the recent interactions were aimed at strengthening opposition coordination.