Calcutta, Feb. 28: The state Congress today reciprocated a CPM gesture by inviting "all the democratic and secular forces in Bengal" to join hands, putting in place the last piece of a jigsaw for shaping a tactical alliance before the Assembly polls.

"On behalf of Pradesh Congress Committee, I am inviting all the democratic and secular forces in Bengal to join together in order to preserve democratic values and to establish the rule of law in West Bengal," a statement by Bengal Congress chief Adhir Chowdhury, issued from Delhi, said this evening.

Although the statement did not name the CPM, state Congress leaders said it had been issued only after the central leadership approved an understanding with the Left in Bengal, a process that had already begun on the ground.

"Whatever has been happening on the ground - joint marches, meetings without flags - hasn't been done keeping the high command in the dark. We were waiting for a signal, and now we have got it," Adhir told The Telegraph tonight.

State Congress veteran and Rajya Sabha member Pradip Bhattacharya echoed him, saying: "It's now official, the high command has given the go-ahead for a tie-up with the Left."

On February 18, the CPM had sought the cooperation of "all democratic forces" in Bengal "to defeat the Trinamul Congress".

Congress sources said that Surjya Kanta Mishra, CPM state secretary and leader of the Bengal Opposition, had conveyed the "urgency" of an understanding to Congress legislative party leader Mohammad Sohrab at the Assembly complex yesterday.

"Sohrab conveyed the information to Adhirda, who later spoke to Surjyababu," a state Congress source said.

He said Chowdhury then contacted the high command's observer for Bengal, C.P. Joshi, who spoke with the central leadership. "The high command authorised Adhirda to issue the statement."

Mamata Banerjee has dared the Congress and the CPM - rivals in Kerala, where polls are due simultaneously with Bengal - to strike a formal alliance. But Congress and CPM sources said a formal tie-up was not needed: ground-level seat adjustments would be enough.

"The CPM central committee has asked the party's state unit to decide the seat shares. Our high command will issue similar instructions. Once that happens, we'll sort out the seats," a state Congress general secretary said.

Trinamul had led from 236 of Bengal's 294 Assembly seats during the last general election, while the Congress and the CPM had led from 21 and 26, respectively. A study of the vote shares shows that a Left-Congress combine would have led from 99 of Trinamul's 236 as well.

CPM sources said the Congress could be offered 70-80 seats. A section in the state Congress wants at least 100 seats but some others say that anything more than the 64 that Trinamul had given the party in 2011 would be acceptable.

CPM insiders said the Congress could be offered the majority of the seats in Malda, North Dinajpur, Jalpaiguri and Murshidabad.

"Our North and South 24-Parganas units are ready to leave five or six seats for the Congress. We are now waiting for the Congress to say something," a source said.

The CPM has told its Left Front partners that they may have to offer a slice of their traditional quota of 80 seats to the Congress.

Sources in both the CPM and the Congress said some seats might be left for eminent people to contest as Independents backed by the two parties.

Although nothing has been finalised, the names doing the rounds include those of retired Supreme Court judge Asok Kumar Ganguly, Jadavpur University professor Ambikesh Mahapatra, retired state chief secretary N. Krishnamurthy and Pankaj Banerjee, former Mamata confidant who quit politics a long time ago.

"Getting people from different fields would mean that both the Congress and the CPM are willing to look beyond their ideological borders to include other voices," said Congress veteran Abdul Mannan.

Trinamul Birbhum chief Anubrata Mondal scoffed at the tie-up efforts.

"(Left Front chairman) Biman (Bose) is a buro bham (old fogey) and Adhir a pakka shaitan (the devil himself). They are forming an alliance but nothing will come of it. The people's alliance is with us," he told a party workers' meeting in Mangalkot, Burdwan.