The Left Front Saturday accused the Congress and the BJP of giving a walkover to Trinamool Congress in West Bengal by fielding weak candidates in large number of constituencies eying a post-poll alliance.Communist Party of India-Marxist (CPI-M) politburo member Surjya Kanta Mishra also accused the ruling Trinamool of a tacit understanding with the Bharatiya Janata Party (BJP)."The Congress and BJP both are giving walkover to the Trinamool by fielding weak candidates, attempting to open avenues for a post-poll alliance. Trinamool had alliances both with the BJP and the Congress in the past. So the polls this time is bi-polar and not four cornered as asserted by many," Mishra, who is also leader of opposition in the assembly, told media persons here.He rubbished Trinamool supremo Mamata Banerjee's claims that the Congress and BJP had formed an alliance with the CPI-M."All her allegations are false and baseless. In fact, it is she who brought in the BJP in the state by tying up with the party in the past. She has this time fielded a former general secretary of the Akhil Bharat Hindu Mahasabha in Varanasi. The Mahasabha is part Rashtriya Swayamsevak Sangh (RSS)," said Mishra.Mishra was referring to Trinamool's Indira Tiwari who will be taking on the might of BJP prime ministerial nominee Narendra Modi from Varanasi.The Marxist leader also ridiculed the Trinamool's manifesto that was launched during the day."It is all about false promises and tall claims, it has no substance," said Mishra.