Samajwadi Party president Mulayam Singh Yadav Friday termed the FIR filed against party general secretary Amar Singh and Bollywood star Amitabh Bachchan as a "conspiracy", and said he sensed that Chief Minister Mayawati had a "hand in it".

"Such a frivolous case against such prominent people could not have been lodged without the connivance of the government and I have reason to believe that the chief minister too has a hand in it, " Mulayam told a press conference here Friday evening.

Terming the FIR registered under the provisions of the Money Laundering Act and the Prevention of Corruption Act, as a "conspiracy", he said: "There can be no doubt that the whole thing is politically motivated."

"Earlier also Mayawati has played dirty against persons associated with the Samajwadi Party, but eventually she failed in her design."

And virtually throwing the gauntlet at the Uttar Pradesh chief minister, the Samajwadi Party chief said: "I challenge these petty conspirators to try whatever they can, but they will not be able to cause the least harm to Amitabh Bachchan or to Amar Singh, whose stature is far too tall to get affected by such acts."

Mulayam Singh also sought to urge the prime minister to intervene and initiate "appropriate punitive action against all those responsible for hatching this conspiracy."

Recalling how the BSP leadership had earlier tried to hound him, he said: "Mayawati got as many as 149 cases lodged against me in one of her earlier stints as chief minister, but not one could pass the judicial scrutiny, which clearly reflects the political motivations behind such moves."

Meanwhile, sticking to his guns, Shivkant Tripathi, the man who filed the police complaint against Amar Singh and Amitabh Bachchan for allegedly laundering illegal money, ruled out any political hand behind the move.

"I am a social activist and chose to take up this issue because it involves a major fraud by people who are icons and political bigwigs, " he told mediapersons in Lucknow.

He said: "If I have lodged the case, it was not without supporting evidence which runs into more than 1, 700 pages of documents, that also depict the stakes Amitabh Bachchan has in the whole affair."

Maintaining that Amar Singh had juggled with balance sheets to siphon away lots of black money, Tripathi said: "If Amar Singh's political mentors were so confident that no fraud had been committed, then why were they so opposed to an open investigation?"

Bachchan and Amar Singh were accused of involvement in a Rs.500 crore money laundering scam, according to a complaint lodged with Kanpur police.