Amid continued setbacks and rebellion involving Trinamool Congress (TMC) since the last assembly election, the party chief in the Indian state of West Bengal has resigned.

Chandrima Bhattacharya, a former minister and three-time MLA in West Bengal and long considered one of the party chief Mamata Banerjee's closest aides, tendered her resignation on Saturday, reports NDTV.

She became the party’s West Bengal president after the election defeat to the Bharatiya Janata Party (BJP) in May, replacing Subrata Bakshi. The appointment came after Mamata had dissolved all party committees and restructured the organisation on Jun 3.

"Please note that I withdraw myself as the authorised signatory of All India Trinamool Congress and all other related organisations in respect of the accounts maintained in various banks. I also withdraw myself from being your authorised person before the Election Commission of India," Chandrima wrote in the resignation letter.

"Where there is no faith, where there is no trust, it is not possible to work. That is why we resigned," the letter adds.

Chandrima, however, said she will always have the highest regard for Mamata.

Soon after the resignation, Chandrima met the party’s rebel faction led by Ritabrata Banerjee at the Bengal Assembly, where the latter was appointed Leader of Opposition despite Mamata endorsing senior TMC MLA Sobhandeb Chattopadhyay for the post.

Reacting to Chandrima’s decision, pro-Mamata MLA Kunal Ghosh questioned why she did not resign "when she had enjoyed plum portfolios given by Mamata Banerjee during her government".

Chandrima was defeated by BJP’s Sourav Sikdar at the Dum Dum Uttar constituency in the assembly elections, according to the PTI.

Her son, Sourav Basu – a former Kolkata Municipal Corporation councillor of the TMC – joined the rebel camp weeks earlier and attended its meetings.

BJP state chief Samik Bhattacharya said: "It doesn't matter anymore which direction the TMC is heading in and which faction is going to take charge of the party. People know TMC has lost its political relevance."

The TMC is embroiled in an existential crisis amid a stunning rebellion within its ranks since the assembly election debacle.

While a majority of its 80 MLAs have broken away and formed a separate group under Ritabrata, 20 of the party's lawmakers have also revolted and declared support for the National Democratic Alliance after merging with the little-known Nationalist Citizens Party of India.