Trinamool Congress chief Mamata Banerjee's efforts to prevent a split in the party and at the same time isolate her colleague Sudip Bandopadhyay has gathered momentum.

"Didi is slowly but surely mobilising the party MPs against him by describing him as greedy and ambitious. He is certainly out of favour and faces an uphill task (in maintaining his position as the party's leader in the Lok Sabha)," a Trinamool member of Parliament told rediff.com over phone from Kolkata.

The Trinamool chief was angry that Bandopadhyay had, a day before the May 25 Cabinet reshuffle, met Deputy Prime Minister Lal Kishenchand Advani and convinced him that he deserved a ministerial berth.

When Banerjee came to know about this, she spread the word that Bandopadhyay was not only unreliable and ambitious, but a risk to the unity of the Trinamool.

She told her party MPs at the party's working committee meeting on May 24 that Bandopadhyay, given his proximity to Bharatiya Janata Party leaders, could no longer be trusted with his position as the Trinamool leader in the Lok Sabha.

The MP said that the BJP leadership's innuendos about which MPs would be accommodated into the Vajpayee government was the final straw for Banerjee.

Terming it as 'betrayal' on the party of Bandopadhyay, she said she would teach him a lesson by canceling her visit to Delhi and sacrificing her own ministerial ambitions.

She rang up Prime Minister Atal Bihari Vajpayee and BJP chief M Venkaiah Naidu to protest that she should have been informed about the proposed induction of Bandopadhyay into the Cabinet. She persuaded Vajpayee to put on hold any induction of Trinamool MPs.

"Mamata canceling her Delhi visit before the Cabinet reshuffle was like cutting off her nose to spite her face. But she has succeeded in snubbing him," said a BJP vice-president.

Since the prime minister has agreed to her entreaty that she would recommend the names of those who should be inducted into the Cabinet after he returns from abroad, Bandopadhyay is out for good, he said.

Banerjee's reconciliation with former Trinamool leader Ajit Panja is another step towards Bandopadhyay's marginalisation.

Panja is recuperating in London and Banerjee's extension of the olive branch to him is bad news for Bandopadhyay. Trinamool sources said that if Panja agrees to return to the Trinamool (right now he is an independent), he could be made the party's leader in the Lok Sabha.

This would force Bandopadhyay to seek greener pastures, the sources said.