The ruling Left Front in West Bengal alleged on Thursday that a "conspiracy" was afoot by various forces including the US to defeat the coalition in the Lok Sabha elections. Left Front chairman Biman Bose referred to the book by former US ambassador to the country,Patrick Moinyham,on how his country had played a role in toppling the E M S Namboodripad government in Kerala in 1957 and the United Front government in West Bengal in 1970. "I warn leftist supporters and party men that these forces are again working for the defeat of left candidates," Bose told a press conference in Kolkata. "Imperialism,Congress,BJP and Trinamool Congress have jointly made the Left Front government the target of their attack," Bose said,while releasing a booklet containing a joint appeal by Left Front constituents to the voters in the state. It said Left Front's return to power for 7th consecutive time with a massive mandate and its strident opposition to the "anti-people" polices of the Congress-led UPA government had made "reactionary" forces within and outside the country "desperate". He charged that with their support,the Trinamool Congress which had allied with the Congress for the Lok Sabha poll was working against the Left Front government. The Left Front also alleged,"The CBI and armed forces were supervising anti-Left activities of opposition forces." Asked how the Left parties which spoke of corruption-free politics could join hands with parties led by J Jayalalithaa and Mayawati who were allegedly involved in graft cases,Bose said an alliance has not been finalised. "So far we have not tied-up with anyone. There are two phases - pre-poll and post-poll arrangement," the CPM Politburo member said. If corrupt people stop indulging in corruption and adopt right policies then there is no problem in working with them," he said. He claimed that the Left parties were working as a driving force behind a non-Congress and non-BJP third alternative at the Centre on the basis of a pro-people economic policy,secularism,independent foreign policy and more powers to states. Bose,who is also the state secretary of the CPM,appealed to the party cadre not to violate the model code of conduct and to erase graffiti if they were written without the consent of house owners.