Facebook has requested that Lina Khan, the new chair of the Federal Trade Commission, step back from deciding whether to pursue an antitrust case against the tech group, marking an escalation in the battle between the regulator’s chief and Silicon Valley’s largest companies.

The social media company filed a petition seeking Khan’s recusal with the FTC on Wednesday, arguing that she “built her career, in large part, by singling out Facebook as a professed antitrust violator”, citing previous criticisms she made of the company.

It is the second such request in two weeks, following a similar petition from Amazon, in a sign of how Big Tech has been rattled by Khan’s appointment.

Facebook said in its request that Khan, “well before becoming a commissioner, had already decided the material facts relevant to Facebook’s liability in the commission’s pending antitrust lawsuit and already reached legal conclusions that Facebook was liable under the antitrust laws”.

The FTC did not comment on the petition.

Khan rose to prominence as an academic by criticising the power of large technology companies, and spearheaded a congressional report last year accusing Google, Facebook, Amazon and Apple of abusing their market power.

As FTC chair, she is at the forefront of an attempt by the Biden administration to tackle the concentration of corporate power in various sectors. She is responsible for the FTC’s high-profile case against Facebook, which it accuses of using its market power to crush smaller rivals.

Filed in December, the lawsuit seeks to undo Facebook’s acquisitions of Instagram and WhatsApp, which the social media giant made in 2012 and 2014 for $1bn and $19bn respectively.

However, a federal judge dismissed the complaint at the end of last month after finding its argument that Facebook had monopoly power over the social network market was “legally insufficient”.

Still, the judge gave the commission a month to file an amended lawsuit if it wished to do so. The impending deadline meant the recusal question was “particularly urgent”, Facebook said in its petition.

Facebook’s petition also pointed to Khan’s work for the Open Markets Institute, an advocacy group, her academic writings and social media posts as evidence that she had “already concluded that Facebook is liable for violating the antitrust laws”.

For example, it highlighted that while Khan was legal director of the Open Markets Institute in 2017, the group led a campaign called Freedom From Facebook, which called for a break-up of the company.

Khan had also “applauded” the FTC for bringing the case last year in tweets that have since been deleted, and accused Facebook of a “copy acquire kill” strategy to preserve its dominance, according to the petition.

Antitrust experts have said that efforts to force Khan’s recusal are unlikely to succeed, as government and agency ethics panels would have already assessed such issues upon her nomination.