PATNA: Describing JD(U), RJD and Congress tie-up as "opportunistic", the three major Left parties in Bihar today formed a grand alliance to contest Assembly by-polls on 10 seats in the state.As per seat sharing agreement, CPI(ML) will contest on five seats, while CPI(M) and CPI will fight on three and two seats, respectively, state secretaries of the three Left parties told reporters at a joint press conference.CPI (M) state secretary Vijay Kant Thakur said, "CPI(ML) will contest Narkatiaganj, Rajnagar (SC), Bhagalpur, Hajipur, Mohania (SC) seats, CPI (M) will put up candidates on Chapra, Mohiuddinagar, Parbatta, while CPI will fight on Jale and Banka."Pointing out that this is the first time that a complete alliance has been formed by the major Left parties in Bihar, CPI state secretary Rajendra Prasad Singh said top Central leaders of the three parties will campaign together for the by-elections.Singh also said that the Left alliance was the need of the hour as the policies of BJP and the JD(U), RJD, Congress were similar and exploitative for the masses.CPI(ML) secretary Kunal described the alliance between JD(U), RJD and Congress as "opportunistic" as they have been fighting against each others all these years."The Left parties can neither be with Congress nor with BJP. Our socio-economic policies are opposed to both these parties, which indulge in exploiting the poor masses," Kunal said.CPI state secretary Rajendra Prasad Singh said that the main aim of the Left alliance was to check the spread of BJP in Bihar.The three Left parties which had contested last Assembly elections separately, had performed badly. Only CPI had managed to win one seat from Sultanganj constituency in Bhagalpur district.CPI and CPI(M) had contested the recent general elections with JD(U), but drew blank.The coming of the three Left parties would try to make the by-polls a triangular contest against the BJP led National Democratic Alliance (NDA) and the alliance of JD(U), RJD and the Congress.