NEW DELHI: The Enforcement Directorate (ED) has written to the Reserve Bank seeking details of forex transactions by firms associated with Tamil Nadu Congress leader Karti Chidambaram and to NSDL seeking info on stock market activities of such firms, two finance ministry officials familiar with the matter told ET. The agency has also sought permission from the finance ministry to send a letter rogatory to Singapore seeking information, these officials said.The flurry of activities is part of a years-long probe into the Aircel-Maxis deal, in which former telecom minister Dayanidhi Maran and his brother Kalanithi, the promoter of Sun Group, are facing trial in a Delhi court.The agency has also informed the Supreme Court, which is monitoring the investigation, that it is closely scrutinising the alleged role of Chidambaram in the Aircel-Maxis case. Prima facie a case can be made out, said the official.Karti denied any connection with the Aircel-Maxis affair. "I do not own a single share in Aircel," he told ET over the phone. Cellular operator Aircel is a subsidiary of Malaysia's Maxis.The focus on Karti, the son of former finance minister and senior Congress leader P Chidambaram, may result in the probe acquiring a political hue.While Karti told ET that he does not ascribe the ED probe to political vendetta against his family, Congress leader Randeep Surjewala said no notices from ED had been received by either Karti or his family members. Surjewala also said there seems to be a "malicious, political vendetta" in the light of another case being registered by the CBI against several Congress leaders, including Sachin Pilot, Ashok Gehlot and Karti Chidambaram.The case being put together by ED centres on two transactions involving Advantage Strategic Consulting Ltd (ASCL), a firm which ED alleges was closely linked to Karti. In one, the valuation at which Advantage Strategic picked up an equity stake in Vasan Healthcare in 2008 is under scrutiny while the other transaction is with Aircel Televentures in 2006. Karti and the firms involved deny any wrongdoing.One of the officials quoted earlier said ED is also probing transactions by 18 firms, which it believes are associated with Karti. While two ASCL officials have been summoned for questioning, Vasan Healthcare officials are likely to be summoned this week.A Rs 26-lakh transaction in 2006, a payment made by Aircel Televentures — then controlled by the Siva Group of C Sivasankaran — to Advantage Strategic, the firm which ED alleges is linked to Karti, is keeping officials in the agency busy.The thrust of the ED investigation appears to be an effort to link Karti to Advantage Strategic. Towards this end, the officials cited earlier refer to the allotment of equity by Advantage Strategic Consulting Limited to Ausbridge Holdings at Rs 15 per share in 2011 as against a book value of Rs 1219.99. This allotment was at a "heavy discount", as per ED's theory, on account of the Rs 26-lakh payment made by Aircel to the firm in 2006. While the shares were priced at Rs 15, Ausbridge paid only Rs 2.5 initially and the rest in calls.Ausbridge Holdings was 95% owned by Karti Chidambaram when it bought 66% stake in Advantage Strategic in 2011.ET had reported in its edition dated May 11, 2012, that Karti owned no shares in ASCL in 2006.ED investigators, according to people familiar with the matter, are thus examining other transactions between entities linked to Karti and his family members and ASCL, going back to 2006 and earlier. The aim of the exercise is to prove Karti's long association with ASCL.In the May 2012 report, ET had also reported that Karti resigned as an Ausbridge director earlier that year. A spokesperson for ASCL had said at the time (May 2012) that Karti did not own any equity in Ausbridge. ET was not able to ascertain when Karti divested his Ausbridge shares.While Karti Chidambaram declined to comment on specific aspects, a spokesperson for Advantage Strategic told ET that the payment was in lieu of consulting services to Aircel."Our company (Advantage Strategic Consulting Pvt Ltd) did a consultancy service to Aircel Televentures in 2006, raised an invoice and received the amount from the client net of TDS (tax deducted at source). Service tax was duly paid, and the transaction was duly reflected in the books of account of the company. The said transaction was done with the party who became the complainant in the case known as ‘Aircel-Maxis case' and not with any of the alleged beneficiaries," the person said.An ED official told ET that the Siva Group, the then owner of Aircel, was unable to furnish any contract or specific details of what service the consultancy rendered to it when questioned by the agency.The Aircel-Maxis affair, which lies at the heart of the case, refers to the controversial acquisition of Aircel by Malaysia's Maxis from C Sivasankaran, a Chennai-based entrepreneur, in 2006. CBI and ED have alleged that Sivasankaran was forced to sell because Dayanidhi Maran, the then telecom minister, held back clearance for spectrum. In return, Maxis, as per the theory of the Indian agencies, bribed the Marans by investing in Sun DTH, part of the Sun Group. BJP leader Subramanian Swamy has often levelled allegations against Karti.The second transaction being investigated by ED is between Advantage Strategic and Vasan Healthcare. In 2008, a 5% equity stake was transferred by Vasan Healthcare to Advantage Strategic for Rs 1.5 crore. The agency says this was a "financial impropriety" and that the transaction was a mere "book entry". The stake, said the officials cited, was substantially undervalued and should have been more than Rs 100 crore. The agency has readied summons to be issued to Vasan Healthcare this week.A spokesperson for Vasan told ET that all its dealings have been in accordance with law. "We categorically state that all our transactions are done in strict legal and accounting compliance and will stand to the utmost scrutiny of law," the spokesperson said.Contradicting ED's line of inquiry, Vasan also asserted that it does not have "any relationship with Apollo Group, Aircel or its promoters". The Reddy family, promoters of the Apollo chain of hospitals, owns a 26% stake in Aircel through Sindya Securities.ED is also investigating transactions between a firm held by Karti Chidambaram's wife, Kriya FMCG Distributors Private Limited, and Sindya Aqua Minerals, held by Suneeta and Dwarkanath Reddy of the Apollo Group. The aim of the exercise again appears intended to prove links between Karti and those associated with the Aircel-Maxis affair.A spokesperson for Advantage Strategic said all transactions were above board and in compliance with law. "All transactions of our company including transactions relating to other entities were done in complete compliance of the laws of the land; all statutory filings were made and we are confident that they will stand the test of legal scrutiny by any statutory authority," the spokesperson for ASCL said.The spokesperson also said it was pursuing a defamation case against BJP leader Subramanian Swamy."It is pertinent to note that a defamation case has been filed by our company against the person who made the baseless and preposterous allegations and the matter is pending in the appropriate forum," the person said. As per the ET report of 2012, Vasan received investments of $150 million from marquee private equity investors such as GIC, the Singapore government's investment arm, Sequoia and Westbridge.