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Two affidavits submitted by Mr Chidambaram's home ministry to the Gujarat High Court in 2009 have pivoted the allegations swirling around the 2004 killing of Ishrat Jehan along with three others in Gujarat by police officers who claimed that she was part of a plot to assassinate Mr Modi, the state's Chief Minister at the time.
The first affidavit on August 6, 2009, said Ishrat, 19, was a "woman activist of the Lashkar-e-Taiba" and the encounter was "not a fit case for a CBI probe." The affidavit quoted Intelligence Bureau inputs, media reports and an apology by a Lashkar mouthpiece as proof of Ishrat's terror links.
A revised affidavit on September 29 said "media reports do not constitute intelligence inputs and intelligence inputs do not constitute conclusive proof." It also stated that the central government would have "no objection" to a CBI investigation into the 2004 encounter.
The home ministry official who drafted both the affidavits - RVS Mani - has alleged that he was "tortured" and pressured by the CBI to name the intelligence officers responsible for inputs on Ishrat's alleged terror links.
Former Home Secretary GK Pillai's charge that Mr Chidambaram bypassed him, "called a lower functionary in the Intelligence Bureau and totally rewrote the affidavit" has also been seized by the BJP.
The BJP alleges that Mr Chidambaram amended the document to suit his Congress party's stand that Ishrat Jehan was innocent and shot in cold blood on the Gujarat government's orders.
"We allege that Chidambaram wasn't doing this on his own. He had orders from the Congress high command to do everything possible to frame Mr Modi and (BJP chief) Amit Shah before the next Gujarat polls," Ravi Shankar Prasad said.
"Mr Chidambaram as Home Minister of India changed an affidavit to say there was no conclusive evidence to prove Ishrat's LeT links. Can a home minister behave in such an irresponsible manner?" he questioned.
Yesterday, Mr Chidambaram said that the revised affidavit was "absolutely correct". "As a minister I accept full responsibility for the affidavit and it is disappointing that the former home secretary who is equally responsible wants to distance himself from that now," he said, reacting to Mr Pillai's allegation.
The home ministry is reexamining the Ishrat case files after the new allegations, which come days after US-based terrorist David Coleman Headley told a Mumbai court that Ishrat was an operative of the Lashkar-e-Taiba.