Peter Navarro, a top White House adviser to Donald Trump, revealed in a court filing on Monday that he had been ordered to testify before a federal grand jury and produce to prosecutors any records concerning January 6, including communications with the former president.

The grand jury subpoena to Navarro, which he said was served by two FBI agents last week, compels him to produce documents to the US attorney for the District of Columbia and could indicate widening justice department action ensnaring senior Trump administration officials.

Navarro’s disclosure about the subpoena came in an 88-page filing that seeks a federal court to declare the House select committee investigating the Capitol attack unlawful, in a desperate move to stop a potential contempt of Congress indictment for defying the panel’s subpoena.

The grand jury subpoena appeared to be part of a case to hold Navarro in contempt rather than pertaining to the justice department’s criminal investigation into the Capitol attack, though the exact nature of the justice department subpoena was not immediately clear.

But the new filing, reviewed by the Guardian, that Navarro will submit to the US district court for the District of Columbia, is not expected to succeed beyond causing a nuisance and possibly delaying the justice department from moving on a contempt indictment.

The filing is seeking the court to rule that the select committee is not properly constituted and therefore illegal, because the House speaker, Nancy Pelosi, refused last year to appoint some Republican members put forward by the House minority leader, Kevin McCarthy.

Since the panel supposedly lacks a Republican minority – despite the presence of Republicans Liz Cheney and Adam Kinzinger – its subpoenas are unenforceable, the suit argues, and therefore his non-compliance with his subpoena is immaterial and should mean the justice department cannot act on a referral for contempt of Congress.

The filing also asks the court to grant an injunction preventing the US attorney for the District of Columbia, Matthew Graves, from enforcing a 28 May 2022 grand jury subpoena compelling him to produce documents requested in the select committee subpoena.

“Since the subpoena of the Committee is ultra vires, unlawful, and unenforceable, the US Attorney’s Grand Jury Subpoena is likewise ultra vires, unlawful, and unenforceable and the US Attorney must be enjoined from any actions to enforce this subpoena,” Navarro wrote.

The argument that the select committee is not properly constituted has been a common charge levelled by some of Trump’s allies against the congressional investigation into January 6, as they seek to find any way to avoid having to cooperate with the sprawling investigation.

But even as Navarro repeats the claim echoed by prominent Republican members of Congress challenging their subpoenas from the panel, he may find his suit an uphill battle given that multiple federal courts have repeatedly rejected that argument as meritless.

Judge Timothy Kelly, a Trump appointee to the DC district court, most recently ruled this month that the panel was not illegitimate when the Republican National Committee mounted a legal challenge to block a subpoena demanding records from its email vendor, Salesforce.

Navarro’s additional argument that Biden could not waive the executive privilege asserted by Trump that precluded him from testifying to the panel is also expected to run into difficulty given the supreme court rejected that reading of the presidential protection.

In the opinion that declined to grant Trump an injunction to stop the National Archives turning over White House documents to the inquiry, the supreme court ruled that although Trump had some ability to assert executive privilege, it did not overcome Biden’s waiver.

The arguments put forward by Navarro are questionable from a legal standpoint, two former US attorneys told the Guardian, broadly characterizing Navarro’s complaint for declaratory and injunctive relief as a frivolous suit designed to buy him time.

A spokesman for the select committee declined to comment.

Navarro was referred to the justice department for criminal contempt of Congress by the full House of Representatives in April after he entirely ignored a subpoena issued to him in February demanding that he produce documents and appear for a deposition.

The top White House trade adviser to Trump was deeply involved in efforts to overturn the results of the 2020 election from the very start, the Guardian has previously reported, deputizing his aides to help produce reports on largely debunked claims of election fraud.

Navarro was also in touch with Trump’s legal team led by Rudy Giuliani and operatives working from a Trump “war room” at the Willard hotel in Washington to stop Biden’s election certification from taking place on January 6 – a plan he christened the “Green Bay Sweep”.