Calcutta, May 4: Bengal Congress working president Sub-rata Mukherjee today announced his decision to return to Mamata Banerjee’s Trinamul Congress.

The move, widely anticipated, comes two days after his secret meeting with Mamata in artist Suvaprasanna’s Salt Lake home where the logistics and terms for his return were worked out.

Mukherjee had joined Trinamul before the Calcutta Municipal Corporation elections in 2000 and became mayor. But he deserted Trinamul before the 2005 civic polls.

“I have decided to quit the Congress and join Trinamul to protest the party’s failure to tie up with Mamata for the (this month’s) Calcutta Municipal Corporation polls,” Subrata said today. He will hold a joint news conference with Mamata tomorrow.

Subrata claimed he had left Trinamul in 2005 to protest Mamata’s stand of not aligning with the Congress for the civic polls. “This time, I am joining her to protest the Congress’s rigid stand of not tying up with her for the civic polls,” he said. “Now, I am certain that the Congress is not serious about ousting the CPM from the state.”

However, sources in the Congress said Subrata had decided to make the switch because he considered Trinamul’s electoral prospects far brighter than the Congress’s.

Sources said the secret meeting on Sunday had discussed two issues: the possibilities of Subrata being given the Rajya Sabha seat that will fall vacant when Swapan Sadhan Bose’s term ends in August 2011 or a “safe” Calcutta seat in the Assembly polls.

It is not known whether Mamata gave any assurance to Subrata, her one-time mentor, on either of the issues, but sources said the Congress leader had emerged “satisfied” from the talks.

Subrata ruled out the possibility of his becoming the mayor this time. “I’m not going to be the mayor,” he said.

Trinamul leaders said Subrata’s switch would help them take on the ruling Left with more vigour during the elections to 81 civic bodies on May 30.

“Subratada’s decision will help us immensely. It is expected to brighten our poll prospects,” said Trinamul general secretary and Union minister of state for shipping Mukul Roy.

That Subrata was mulling a jump had become evident from the way he was distan-cing himself from Congress managers closing ranks and fighting to contain rebellion against Mamata’s offer of only 25 wards of the 141 in Calcutta.

The state Congress working president was conspicuous by his absence on Saturday when the party released its list of 88 candidates for Calcutta civic body.

Then he left a clearer hint about his intentions when he said he would campaign for his sister Tanima Chatterjee, a Trinamul candidate from Ward 87. Subrata had represented this ward as the mayor of Calcutta.

“My younger sister has requested me to campaign for her,” Mukherjee had told The Telegraph yesterday. “As her elder brother, how can I turn it down?”

But today, once he made public his decision to switch sides, Subrata said he would campaign for all Trinamul candidates and not just his sister.

Congress leaders called his move a “forgone conclusion”.

“His desertion will not have an impact on the Congress,” said the other state Congress working president, Pradip Bhattacharya. “In any case, we were all prepared for it.”

In private, a Congress leader admitted that Subrata was an “an organisational leader who also has a workers’ support base being the head of Intuc. “His departure is bound to have some impact on the party.”