Tensions between the US justice department and the House of Representatives January 6 select committee have escalated after federal prosecutors complained that their inability to access witness transcripts was hampering criminal investigations into rioters who stormed the Capitol.

The complaint that came from the heads of the justice department’s national security and criminal divisions and the US attorney for Washington Matthew Graves showed a likely collision course for the parallel congressional and criminal probes into the Capitol attack.

“The interviews the select committee conducted are not just potentially relevant to our overall criminal investigations, but are likely relevant to specific prosecutions,” Graves wrote, alongside assistant attorneys general Kenneth Polite and Matthew Olsen.

“The select committee’s failure to grant the department access to these transcripts complicates the department’s ability to investigate and prosecute those who engaged in criminal conduct in relation to the January 6 attack on the Capitol.”

Federal prosecutors are seeking all of the select committee’s transcripts as they quietly expand their criminal inquiry into January 6 rally organizers and people in Donald Trump’s orbit, according to a source familiar with the matter and grand jury subpoenas reviewed by the Guardian.

The justice department has empaneled one grand jury in Washington to investigate the rally organizers, examining whether any executive or legislative branch officials were involved in trying to criminally obstruct Joe Biden’s congressional certification.

Another grand jury also appears to be investigating political operatives and lawyers close to Trump, including the ex-president’s former attorney Rudy Giuliani, over their involvement in a scheme to send fake Trump electors to Congress on January 6.

The justice department has also signaled a potential interest in moving more aggressively with Capitol attack related prosecutions. The US attorney general, Merrick Garland, said this week that he and federal prosecutors were closely watching the select committee’s hearings on Capitol Hill.

But the panel has been reluctant to work with the justice department, in part because of fears that they lose control over their work product once they release the transcripts or that prosecutors might misinterpret their evidence, according to a source close to the inquiry.

The chairman of the select committee, Bennie Thompson, said on Thursday that the panel would eventually cooperate with the justice department but the panel was “not going to stop what we are doing to share the information that we’ve gotten … We have to do our work.”

The public repudiation by top justice department officials – the letter came during the panel’s third hearing into the Capitol attack – marks the latest point in steadily worsening relations ahead of looming trial dates for members of the far-right Proud Boys group on seditious conspiracy charges.

Federal prosecutors said they were seeking witness transcripts as part of their preparations for an expected trial in September of five top Proud Boys members charged with seditious conspiracy and obstructing an official proceeding on January 6.

The justice department’s complaint was included in a court filing as part of prosecutors’ notice to the judge that they agreed with defendants’ request to delay trial because of a lack of access to the panel’s witness transcripts.

US district judge Timothy Kelly set a hearing on the matter for next Wednesday after a lawyer for one of the Proud Boys, Ethan Nordean, objected to the trial delay. Kelly gave former Proud Boys leader Henry Tarrio and another defendant until Monday to say whether they also objected to the request.