In a realignment of forces in the wake of Congress and Samajwadi Party coming together, the Left parties on Sunday made a common cause with the Bahujan Samaj Party by roping in Mayawati in the opposition to the Indo-US nuclear deal.

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Reaching out to the ruling party in Uttar Pradesh, which has 17 MPs in the Lok Sabha, Communist Party of India-Marxist General Secretary Prakash Karat drove to the Uttar Pradesh chief minister's residence in New Delhi to hold the first meeting after the Left parties withdrew support to the United Progressive Alliance government over the nuclear deal.

The two parties decided to cooperate to ensure defeat of the Congress-led government during confidence vote in the Lok Sabha on July 22.

After the 45-minute meeting, the Marxist leader hailed Mayawati's opposition to the nuclear deal and said the two sides decided that they should cooperate in the 'struggle' against the accord.

"Mayawati reiterated her opposition to the deal. It was decided that there should be cooperation to stop the deal and in the struggle against the UPA government in this regard," Karat said.

Sources said the Left parties opened channels of communication with Mayawati three days back with top CPI leadership seeking her cooperation in the fight against government.

Significantly, Karat's meeting with Mayawati came a day after the CPI-M condemned the filing of a fresh affidavit by CBI against the BSP chief in a disproportionate assets case.

The CBI action was also condemned by CPI, whose general secretary, A B Bardhan, raised questions over the timing of filing of the affidavit.

Bardhan said the Left parties are in touch with Mayawati, who has assured them that BSP will vote against the government during the trial of strength.

Suggesting that the government was using CBI as a 'political tool' against Mayawati, Bardhan said the country's premier probe agency is 'being used to switch off or switch on its so-called investigation and prosecution and launch cases just as this moment according to what will help the ruling party to rig up a majority'.

After the SP, with 39 MPs dumped them, the Left parties have been trying to reach out to other parties, which include TDP, TRS and JD(S). Left has 59 MPs in the Lok Sabha.

Karat had on July 11 said he was in touch with 'all parties', which can take a stand against the deal, an issue on which the Left parties withdrew support to the government reducing it to a minority.