One faction of the party remained loyal to its founder and chairperson, Mamata Banerjee, and her nephew and general secretary, Abhishek Banerjee. The other—led by Ritabrata Banerjee and fellow Member of Legislative Assembly (MLA) Sandipan Saha—positioned itself as the party's legislative wing in the new assembly and aligned with the Bharatiya Janata Party-led National Democratic Alliance.
Background
On 4 May 2026, after the 2026 West Bengal assembly polls result was declared, 15-year ruling AITC government led by the founder-chairperson of the party and then Chief Minister of West Bengal, Mamata Banerjee lost the power from the state and for the first time, the India's ruling party, Bharatiya Janata Party came to power in the state with former Trinamool leader and once Mamata's close aide Suvendu Adhikari succeeding as Chief Minister on 9 May, after Mamata. Mamata Banerjee herself lost her seat, Bhabanipur, to her successor, Adhikari.
After the defeat, Mamata Banerjee called a meeting of winning candidates in her residence in Kolkata, but out of 80 winning candidates, only 66 were present. Soon after, on 11 May, the party leadership declared former senior minister and newly elected AITC MLA from Ballygunge, Sovandeb Chattopadhyay, as the Leader of Opposition through a letter by Abhishek Banerjee, the party's General Secretary. But two AITC MLAs, namely Ritabrata Banerjee from Uluberia Purba and Sandipan Saha from Entally, allegedly complained to the Speaker of the Legislative Assembly, Rathindra Bose, that the MLAs' signatures on the letter are forged. On 22 May, during CM Suvendu's tour to New Delhi, Ritabrata and Suvendu held a secret meeting at Banga Bhawan.
Meanwhile, many councillors in various municipalities such as Bhatpara, Contai, and North Barrackpur resigned. In Chandannagar, the entire municipal board was dissolved after councillors and the mayor resigned. Soon after, on 26 May, MP from Barasat, Kakoli Ghosh Dastidar resigned from various AITC organisational posts, taking responsibility for the party's defeat. After her resignation, she attended CM Adhikari's administrative meeting in Kalyani with 20 elected AITC MLAs, including Swarupnagar MLA Bina Mondal, Haroa MLA Abdul Matin Muhammad, and Deganga MLA Anisur Rahaman Bidesh.
On 1 June 2026, Ritabrata and Sandipan were permanently suspended from the party for publicly insulting Abhishek Banerjee for defeat. Various spokespersons, including Riju Dutta, Kohinoor Mazumder, and Supriyo Chanda, were suspended from the party following their comments favouring the BJP government and Suvendu, and allegedly for anti-party activities such as openly blaming Abhishek Banerjee across various media platforms. Two Kolkata Municipal Corporation councillors, Arup Chakraborty and Susanta Ghosh, also resigned from their posts.
Following the suspension of the rebel legislators, 60 MLAs declared their support for the Ritabrata Banerjee-led faction, which was subsequently recognised by Speaker Rathindra Bose as the principal opposition bloc in the West Bengal Legislative Assembly. Ritabrata Banerjee replaced Sovandeb Chattopadhyay as Leader of the Opposition. The list of supporting MLAs was submitted to the Speaker. The split resulted in competing claims over the organisation and leadership of the All India Trinamool Congress, with the rebel faction subsequently forming a parallel organisational structure. On 22 June, the faction held a special session at which Arup Roy was elected chairperson and a 30-member National Working Committee was constituted, while the Mamata Banerjee-led faction continued to recognise Banerjee as party chairperson.
Following the rebellion in legislative assembly,
a separate split occurred within the TMC's Lok Sabha parliamentary party. In June 2026, 20 of the party's 28 Lok Sabha MPs, led by Kakoli Ghosh Dastidar, broke away from the TMC parliamentary group and sought recognition as a separate bloc in the Lok Sabha. The group submitted a representation to Speaker Om Birla and announced that it would merge with the Nationalist Citizens Party of India (NCPI). The merger was accompanied by an announcement that the MPs would support the National Democratic Alliance (NDA) government at the centre. The rebel MPs also stated that they intended to continue their claim to the TMC's original name and election symbol before the Election Commission.
Rajya Sabha split, resignation and BJP re-election
The split was followed by a separate wave of resignations from the Rajya Sabha. Sukhendu Sekhar Roy resigned from both the TMC and his Rajya Sabha seat on 8 June 2026, citing the party's mismanagement during the election, followed by Sushmita Dev and Prakash Chik Baraik in the following days. The three resignations created vacancies in three Rajya Sabha seats from West Bengal. On 9 July, Roy, Dev and Baraik joined the Bharatiya Janata Party and were subsequently nominated by the party for the Rajya Sabha by-elections to the seats they had vacated. On 17 July, all three were elected unopposed to the Rajya Sabha as BJP candidates.
ECI action and new symbols
On 2 July 2026, Ritabrata, Sandipan, and eight other MLAs went to Delhi to meet Chief Election CommissionerGyanesh Kumar to claim the party symbol and name, along with its funds.
On 17 September 2026, ahead of the by-elections announced for Nandigram and Rejinagar, the Election Commission of India (ECI) issued an interim order recognising the existence of two rival groups within the All India Trinamool Congress and froze the party's name and its reserved "Flowers and Grass" symbol pending a substantive determination under Paragraph 15 of the Election Symbols (Reservation and Allotment) Order, 1968. The commission directed both factions to contest the by-elections under separate names and symbols. On 18 September, the ECI allotted the name Mamata All India Trinamool Congress and the "Football Player" symbol to the faction led by Mamata Banerjee, while the faction led by Arup Roy was allotted the name Democratic Trinamool Congress and the "Envelope" symbol. The allotments were made as an interim arrangement for the by-elections and did not constitute a final determination of which faction was entitled to the original party name and symbol.
The Rebels have announced a temporary merger with the NCPI and will fight for legitimacy as the Real AITC in the Supreme Court. On 14 June 2026, Dastidar and other MPs, announced their merger with the NCPI.
The Split first occurred in the Legislative Assembly when Ritabrata Banerjee and Sandipan Saha complained to the Speaker of the West Bengal Legislative Assembly and secured support of 65 MLAs, including their signatures, for appointing Ritabrata as the leader of the opposition.
The following are some of the names of the MLAs who have rebelled:
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