NEW DELHI: Investigations into the alleged involvement of former FM P Chidambaram in the INX Media case are relying on a key claim by his son’s chartered accountant that a shell company , also controlled by Karti Chidambaram, allegedly paid for his “travel bills” and “certain expenses”.ET has reliably gathered that Karti’s chartered accountant Bhaskar Raman , who is also an accused in the case, claimed this in his testimony before the Enforcement Directorate (ED) on May 22 last year. He alleged this when confronted by documents and hard disks seized from the Chennai premises of Karti-promoted Chess Global Advisory Services Pvt Ltd.These documents detailed expenses borne by Advantage Strategic Consulting Private Ltd (ASCPL). There is repeated mention of “PC Sir” under a column titled “work”. The documents also link Chess Global to ASCPL Karti has so far denied any association with ASCPL, unlike Chess Global where he is a promoter-director. Chidambaram too has categorically denied knowledge of ASCPL or its antecedents.Bhaskar Raman has stated in his testimony that “PC Sir” referred to P Chidambaram, reliable sources told ET.Sources said Chidambaram, during his questioning, has strongly denied receiving any payments for travel or other expenses from ASCPL.Queried about Bhaskar Raman, Chidambaram is believed to have said that he knew of him because his own chartered accountant might have consulted Raman as a professional. Bhaskar Raman is one of the shareholders in ASCPL.Those aware of the details of Bhaskar Raman’s testimony told ET that the statement was recorded under Section 50 of the Prevention of Money Laundering Act (PMLA), which is admissible in the court.To ascertain proceeds of crime allegedly parked abroad by the accused in the case, the Central Bureau of Investigation has written letters rogatory to five countries — the United Kingdom, Bermuda, Switzerland, Mauritius and Singapore.Both Chess Global Advisory and ASCPL are accused of receiving bribes for Karti in the garb of consultancy services.Probe agencies allege that Karti received kickbacks through these two companies to influence Foreign Investment Promotion Board (FIPB) approvals in violation of rules for foreign direct investment when Chidambaram was the finance minister.Karti has denied these allegations. He was granted bail last year by the Delhi High Court on the ground that probe agencies did not have sufficient evidence to prove that he met any of the then FIPB members.Chidambaram is currently in CBI custody. He will be produced before a special CBI court on August 26, where the agency is likely to seek further custody for interrogation.