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Investigators say Mr Chidambaram violated laws by sanctioning a Rs 3,500-crore deal that saw Malaysia's Maxis buying telecom company Aircel in 2006. Mauritius-based Global Communication Services Holdings -- a subsidiary of Maxis - had sought approval to invest in Aircel.
The investment should have been cleared by the Cabinet Committee on Economic Affairs headed by the Prime Minister but was instead signed off by the Finance Ministry, which only has the power to sanction smaller investments. After the approval, Aircel Televentures Limited paid Rs 26 lakh to a company linked to Karti Chidambaram.
The former minister asserts that all investment approvals granted during his tenure were above board. He has linked the charges to his criticism of Prime Minister Narendra Modi and his government.
"CBI has already filed a chargesheet in the Aircel-Maxis case. ED has now filed a complaint in the same case. If and when summons is issued by the Honourable Court, the cases will be contested. I will not make any other public comment," Mr Chidambaram tweeted.
The Enforcement Directorate filed the chargesheet a day before its chief Karnail Singh retires; sources say he wanted to oversee progress on an important case before signing out.
Mr Chidambaram and his son were named in the CBI's chargesheet. The Enforcement Directorate's earlier chargesheet named only Karti. Today, it filed a supplementary chargesheet that will be taken up a month later.
Karti Chidambaram, 46, had been arrested in February on charges of money-laundering in the same case but was granted bail. Both father and son were questioned by the Enforcement Directorate.
This morning, Mr Chidambaram had been given a reprieve in another case, involving INX Media, as his protection from arrest was extended by a court till November 29.
The INX Media case involves a deal dating to 2007 when foreign investment go-ahead was given to the media company then owned by Indrani and Peter Mukerjea, who are now both in jail on charges of murdering her daughter from a previous relationship.
The CBI earlier failed to prove its case that former Telecom Minister Dayanidhi Maran had forced Aircel owner C Sivasankaran to sell the company to Maxis, which is owned by T Ananda Krishnan, a tycoon based in Malaysia. Mr Maran, of the DMK, had been accused of holding up vital clearances and licenses for Aircel till its owner succumbed to pressure to sell to Maxis.