On Oct. 6, The Wall Street Journal reported that activist investor group Starboard Value owns a stake in Pfizer ( PFE -0.61%) that's worth approximately $1 billion. Now, Starboard will aim to work with the company's management as well as consult with former executives -- all with the aim of turning around Pfizer's sagging fortunes.

The ongoing corporate battle between Pfizer and activist investment firm Starboard Value escalated on Thursday when Starboard pushed Pfizers board to investigate alleged coercive actions. This follows the

Activist investor Starboard Value claims the pharma giant’s former CEO and CFO were “threatened” into backing current management.

Pfizer Inc. company officials threatened legal action against two former top executives who had been working with Starboard Value to push for changes at the drugmaker, the activist investor alleged Thursday in a letter to the company’s board.

Pfizer’s situation with activist investor Starboard Value is already getting messy. | After initially supporting a meeting with activist investor Starboard Value, Pfizer's former CEO and CFO publicly changed their tune after being threatened with litigation by Pfizer,

As the battle over Pfizer’s future continues, former executives said they would no longer support activist investor Starboard Value.

Starboard has accused Pfizer of “coercive conduct” after executives who initially backed the hedge fund retracted their support.