A veteran FBI agent who wrote derogatory, lewd text messages about President Donald Trump filed a lawsuit Tuesday charging that the bureau caved to “unrelenting pressure” from the president when it fired him.

The suit from Peter Strzok also alleges he was unfairly punished for expressing his political opinions, and that the Justice Department violated his privacy when it shared hundreds of his text messages with reporters.

Strzok’s messages included promises to “stop” Trump durign the election, and also said he had “an insurance policy” prepared against the Trump administration after the 2016 presidential election results were known. Strzok was a key member of special counsel Robert Mueller’s probe, and authorized the controversial FISA wiretap warrants of Trump Tower during the 2016 presidential campaign.

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Trump has referred to Strzok’s messages as proof of the so-called “Deep State” trying to undermine his adminsitration.

The complaint, which names as defendants Attorney General William Barr and FBI Director Chris Wray, revisits a political drama that was seized on by conservative critics of Mueller’s Russia investigation as proof that the bureau was biased against Trump. It provides new details about the circumstances of Strzok’s firing, coming months after a fiery congressional hearing in which he insisted that his personal views never influenced his work.

Multiple investigations are underway examining whether the FBI acted improperly during the Russia investigation, and Strzok remains a frequent target of Trump’s scornful tweets. A Justice Department inspector general report focused on the early days of the Russia probe is expected to be released in the coming weeks.

Spokespeople for the FBI and the Justice Department declined to comment on Strzok’s lawsuit.

Strzok was removed from Mueller’s team after the texts with FBI lawyer Lisa Page, his former lover, came to light. He was fired from the FBI last August.

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The lawsuit seeks reinstatement to the FBI, back pay and a declaration that the Trump administration violated his rights.

Many of the texts, on FBI cell phones, were bitingly critical of Trump during his 2016 run for office. They were found by the department’s inspector general during its investigation of the FBI’s Clinton email probe. The watchdog office criticized both Strzok and Page for their judgment in sending the messages but didn’t reach a conclusion that the Clinton email investigation was tainted by political bias.

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The Associated Press contributed to this article