In a letter sent Monday to Joseph W. Koufari, the agency’s inspector general, the heads of two congressional committees said they had developed “serious new concerns about the lack of transparency and independence that appear to compromise the integrity of a critical investigation from your office.” The letter from Representative Carolyn B. Maloney, D-New York, and chairman of the Oversight Committee, and Representative Bennie Thompson, D-Mississippi, and chairman of the Homeland Security Committee, renewed the couple’s demand made last week by Mr. Cuffari withdraw from the survey. He also called two of his office’s top officials to testify this month. The inspector general’s office did not immediately respond to a request for comment. It was the latest twist in a drama about text messages sent and received by Secret Service agents at the time of the Capitol Hill uprising. Mr Cuffari told the House committee investigating the January 6 attack last month that the messages had been deleted, suggesting it happened as part of a device replacement program and that the department had stopped looking into what happened because it was the subject of a criminal investigation. He said those whose messages were missing include agents who were part of former President Donald J. Trump. In Monday’s letter, Ms Maloney and Mr Thompson, who also heads the January 6 committee, wrote that their committees had gathered “new evidence” that Mr Cuffari’s office had “surreptitiously abandoned efforts to collect text messages from the Secret Service more than a year ago.” They added that his office “may have taken steps to cover the extent of the missing records, raising further concerns about your ability to independently and effectively carry out your duties as inspector general.” The lawmakers’ letter cited reports from CNN that the inspector general learned in May 2021 — seven months earlier than previously disclosed — that the Secret Service was losing critical text messages. The letter also said the committees learned that Mr. Cuffari’s office was notified in February that text messages from Chad Wolf and Kenneth T. Cuccinelli II, the two top policy officials at the Department of Homeland Security on Jan. 6, 2021, could don’t have access. They added that the inspector general also knew that Mr. Cuccinelli was using his personal phone and also failed to collect messages from that device. Mr Wolf tweeted that he had “complied with all data retention laws and returned all my equipment fully loaded to the Department. Perfect. DHS has all the texts, emails, phone logs, schedules, etc. Any issues with missing data should be directed to DHS.” Lawmakers have since raised questions not only about the missing text messages, but why Mr. Cuffari did not notify Congress sooner or take steps to retrieve them sooner. The committees received a July 27, 2021 email from Thomas Kait, deputy inspector general, stating that “we are no longer requesting phone records and text messages from the USSS regarding the events of January 6.” He used the abbreviation for the United States Secret Service. Lawmakers also said their committees had gathered evidence that just four months later, on Dec. 3, 2021, the inspector general finally made a new request to the department for some text messages. Mr. Kait, they said, removed key language from a February 2022 memo that emphasized the importance of text messages and criticized the department for not complying with the Dec. 3, 2021, request. Ms. Maloney and Mr. Thompson invited Mr. Kait and Kristen Fredricks, the office’s chief of staff, to sit for interview transcripts until August 15. Mr Cuffari sparked a firestorm on Capitol Hill last month when he said the text messages had been deleted, even after he had requested them as part of an investigation into the events of January 6. The Secret Service disputed parts of the inspector general’s findings, saying it “lost” data on “some phones” as part of a pre-planned three-month “system migration” in January 2021, but insisting that no texts related to the investigation “were lost in immigration”. The agency said the project was underway before it received notice from the inspector general to retain its data and that it did not delete “malicious” text messages. In response, the committee on Jan. 6 subpoenaed the Secret Service seeking text messages from Jan. 5 and 6, 2021, said to have been deleted, as well as any post-action reports. The Secret Service said it may not be able to recover a batch of deleted text messages from phones used by its agents during the attack on Capitol Hill last year, but it had turned over “thousands of pages of documents” and other files related to decisions that received on January 6. Representative Jamie Raskin, D-Maryland and a member of the Jan. 6 committee, said it appeared the inspector general was “extremely late in reporting this appalling situation for a long time.” “It’s getting to the point where inspectors general need inspectors general,” he said. “It just seems like an egregious dereliction of duty on his part.”