Facebook is facing legal action from US regulators and more than 45 state prosecutors.
The social networking platform has been accused of taking illegal actions to buy up rival firms and in the process, reduce its competition.
However, Facebook general counsel Jennifer Newstead has pointed out that the deals in question were all previously approved by regulators in the US.
She said: "The government now wants a do-over, sending a chilling warning to American business that no sale is ever final."
Newstead insisted that the company would do everything it could to defend its interests and its reputation.
The lawsuits filed by the states and Federal Trade Commission centre on the tech giant's acquisition of Instagram in 2012 and WhatsApp in 2014.
The case also cites an internal message from Facebook owner Mark Zuckerberg in 2008, when he said it was "better to buy than compete".
Letitia James, the New York Attorney General, has warned of the potentially negative impact of Facebook's power and influence.
James said: "For nearly a decade, Facebook has used its dominance and monopoly power to crush smaller rivals and snuff out competition, all at the expense of everyday users.
"No company should have this much unchecked power over our personal interaction and social interactions. That's why we are taking action today."
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