The latest sniping came days after stock in Reliance ADA, Anil Ambani's conglomerate, lost $2.5 billion in value in a single late-session plunge.
The group called on regulators to investigate a "vicious and illegal bear hammering of our listed stocks", following a selloff that helped make group flagship RCOM the worst performer this year in India's main Sensex index.
RCOM's shares are 88 percent below their early 2008 peak and hit an all-time low last week.
Its profit has declined for six straight quarters, and it had net debt of $7 billion in December, versus a market value of $4.5 billion.
"I think he is an ideal target for any slander campaign because his company is weak, it's leveraged and the reputation has been tarnished," said Eric Mookherjee, a Paris-based fund manager with Shanti India.
"Anil is a less powerful man than he was - at least that's the impression I have," he said.