Originally Published: 26 JUL 22 15:45 ET

Updated: 26 JUL 22 15:47 ET

By Whitney Wild and Jeremy Herb, CNN

(CNN) -- Two top House Democrats are calling for the Department of Homeland Security inspector general to recuse himself from the investigation into Secret Service text messages, saying his failure to inform Congress for months that messages, saying they lost confidence after he failed to inform Congress for months that messages around January 6 may have been erased.

House Oversight Chairwoman Carolyn Maloney and House Homeland Security Chairman Bennie Thompson -- who also chairs the House January 6 committee -- wrote to DHS inspector general Joseph Cuffari Tuesday, saying his failure to tell Congress the Secret Service wasn't providing records "cast serious doubt on his independence and his ability to effectively conduct such an important investigation."

"These omissions left Congress in the dark about key developments in this investigation and may have cost investigators precious time to capture relevant evidence," the Democrats wrote. "There must be no doubt that the Inspector General leading this investigation can conduct it thoroughly and with integrity, objectivity and independence. We do not have confidence that Inspector General Cuffari can achieve those standards."

In the letter, the lawmakers wrote that the inspector general told Congress in November 2021 that DHS "significantly delayed" access to records related to the review of January 6, but that the inspector general failed to say that the Secret Service was the reason. In addition, Cuffari was informed in December 2021 that text messages "sent and received by Secret Service agents related to the events of January 6 had been erased," Maloney and Thompson wrote.

"Yet, Inspector General Cuffari took no steps to inform Congress of this serious and flagrant violation of federal records laws," the lawmakers said. "The DHS IG's failure to promptly report and escalate the Secret Service's stonewalling calls into question whether Inspector General Cuffari has the professional judgment and capacity to effectively fulfill his duties in this investigation."

The Democrats' letter underscores the tensions between the inspector general and the Democratic committees after the Secret Service text message issue spilled into public view two weeks ago. Since then, the House select committee issued a subpoena to the Secret Service over the texts -- but the inspector general instructed the agency to stop its own investigation because of the inspector general's own "ongoing criminal investigation."

CNN has reached out for comment to the inspector general's office.

On July 14, Cuffari told the House and Senate Homeland Security committees that DHS "notified us that many US Secret Service text messages from January 5 and 6, 2021, were erased as part of a device-replacement program."

The following day, Cuffari briefed the House select committee, and the panel issued a subpoena shortly thereafter for records from the Secret Service.

Cuffari was appointed by former President Donald Trump in 2019 to lead the DHS inspector general's office, and he faced criticism when he chose in 2020 not to investigate the appointments of top acting DHS officials in the Trump administration.

Cuffari is also the subject of an investigation being led by the Council of Inspectors General on Integrity and Efficiency (CIGIE), a federal government umbrella group tasked with fielding allegations made against an inspector general. The probe stems from accusations of retaliation related to the authorization of an independent report by law firm WilmerHale that was concluded in late 2020 following complaints of unprofessional behavior by several top Homeland Security officials.

In late 2020, WilmerHale completed its independent investigation into allegations that several senior employees engaged in an assortment of unprofessional behavior "that was designed to undermine and contravene the authority of the two Inspector Generals (IGs) to whom they reported at DHS OIG from late 2017 to 2020."

Maloney and Thompson sent their letter on Tuesday to Cuffari and Allison Lerner, who chairs the inspectors general umbrella group.

The Democratic chairs added that it was "not the first time" Cuffari had been unwilling to investigate the agency.

"According to reports, Inspector General Cuffari previously refused to investigate the Secret Service's actions surrounding excessive use of force, as well as its protocols on protecting officials during the coronavirus pandemic, contradicting recommendations from DHS OIG career staff," they wrote.