Mistry, who is locked in a boardroom tussle with the Tatas, alleged Singh had a role in the AgustaWestland chopper scam as it happened when he was the Defence Secretary in 2010.
"As Defence Secretary, Singh was a key official involved in award of Rs 3600 crore VVIP helicopter contract to AugustaWestland in 2010," Mistry's office said in a statement in Mumbai.
Singh, however, rejected the charge, saying the deal was approved by the Union Cabinet well after he had retired from government service.
"To connect me with this matter is slanderous and malicious," Singh, an independent director on Tata Sons board, said.
Disclaimer: No Business Standard Journalist was involved in creation of this content