WASHINGTON — Two influential Home Democrats known as on Monday for 2 officers on the Division of Homeland Safety’s unbiased watchdog to testify to Congress concerning the company’s dealing with of lacking Secret Service textual content messages from the day of the Jan. 6 assault on the Capitol, accusing their workplace of partaking in a cover-up.

In a letter despatched Monday to Joseph V. Cuffari, the company’s inspector common, the heads of two congressional committees stated that they had developed “grave new issues over your lack of transparency and independence, which look like jeopardizing the integrity of a vital investigation run by your workplace.”

The letter from Consultant Carolyn B. Maloney, Democrat of New York and the chairwoman of the Oversight Committee, and Consultant Bennie Thompson, Democrat of Mississippi and the chairman of the Homeland Safety Committee, renewed a requirement the pair made final week that Mr. Cuffari step other than the investigation. It additionally known as for 2 of his workplace’s high workers to testify this month.

The inspector common’s workplace didn’t instantly reply to a request for remark.

It was the most recent flip in a drama over what turned of textual content messages despatched and acquired by Secret Service brokers across the time of the Capitol riot.

Mr. Cuffari final month knowledgeable the Home committee investigating the Jan. 6 assault that the messages had been erased, suggesting that it occurred as a part of a tool alternative program, and that the division had ceased trying into what turned of them as a result of they had been the topic of a legal investigation. He has stated these whose messages had been lacking included brokers who had been a part of former President Donald J. Trump’s safety element.

Within the letter on Monday, Ms. Maloney and Mr. Thompson, who additionally leads the Jan. 6 panel, wrote that their committees had obtained “new proof” that Mr. Cuffari’s workplace had “secretly deserted efforts to gather textual content messages from the Secret Service greater than a 12 months in the past.” They added that his workplace “might have taken steps to cowl up the extent of lacking data, elevating additional issues about your means to independently and successfully carry out your duties as inspector common.”

The lawmakers’ letter cited reporting from CNN that the inspector common discovered in Could 2021 — seven months sooner than beforehand revealed — that the Secret Service was lacking essential textual content messages.

The letter additionally said that the committees had discovered that Mr. Cuffari’s workplace was notified in February that textual content messages from Chad Wolf and Kenneth T. Cuccinelli II, the highest two political officers on the Division of Homeland Safety on Jan. 6, 2021, couldn’t be accessed. They added that the inspector common was additionally conscious that Mr. Cuccinelli was utilizing his private cellphone and in addition failed to gather messages from that system.

Mr. Wolf wrote on Twitter that he “complied with all information retention legal guidelines and returned all my gear totally loaded to the Division. Full cease. DHS has all my texts, emails, cellphone logs, schedules, and so forth. Any points with lacking information must be addressed to DHS.”

Since then, the lawmakers have raised questions on not simply the lacking textual content messages however why Mr. Cuffari didn’t alert Congress sooner or take steps to retrieve them earlier.

The committees obtained a July 27, 2021, e-mail from Thomas Kait, a deputy inspector common, stating that “we now not request cellphone data and textual content messages from the USSS referring to the occasions on January sixth.” He used the abbreviation for the US Secret Service.

The lawmakers additionally stated their panels had gathered proof that it was not till 4 months later, on Dec. 3, 2021, that the inspector common lastly submitted a brand new request to the division for sure textual content messages.

Mr. Kait, they stated, eliminated key language from a February 2022 memo that highlighted the significance of the textual content messages and criticized the division for failing to adjust to the Dec. 3, 2021, request.

Ms. Maloney and Mr. Thompson known as on Mr. Kait and Kristen Fredricks, the workplace’s chief of employees, to sit down for transcribed interviews by Aug. 15.

Mr. Cuffari prompted a firestorm on Capitol Hill final month when he reported that the textual content messages had been erased, even after he had requested them as a part of an inquiry into the occasions of Jan. 6.

The Secret Service disputed components of the inspector common’s findings, saying that it “misplaced” information on “some telephones” as a part of a preplanned three-month “system migration” in January 2021, however insisting that no texts pertinent to the inquiry “had been misplaced within the migration.” The company stated that the challenge was underway earlier than it acquired discover from the inspector common to protect its information, and that it didn’t “maliciously” delete textual content messages.

In response, the Jan. 6 committee issued a subpoena to the Secret Service looking for textual content messages from Jan. 5 and 6, 2021, that had been stated to have been erased, in addition to any after-action studies.

The Secret Service stated it may not be capable of get better a batch of erased textual content messages from telephones utilized by its brokers across the time of the assault on the Capitol final 12 months, however had delivered “hundreds of pages of paperwork” and different data associated to choices made on Jan. 6.

Consultant Jamie Raskin, Democrat of Maryland and a member of the Jan. 6 committee, stated it appeared that the inspector common “was extraordinarily tardy in reporting this egregious scenario for a very long time.”

“It’s attending to the purpose the place inspectors common want inspectors common,” he stated. “It simply looks like a scandalous dereliction of obligation on his half.”