 -- House Democrats are raising concerns about the security clearance held by President Trump’s son-in-law and senior adviser Jared Kushner, saying suspicions about his contacts with Russian officials should be enough to suspend his access to sensitive information.

“When there are credible allegations that employees may be unfit to continue accessing classified information, security clearances are supposed to be suspended while the allegations are investigated,” wrote Rep. Elijah Cummings, the ranking Democrat on the House Oversight Committee, in a letter to White House chief of staff Reince Priebus. “Mr. Kushner reportedly failed to disclose contacts with dozens of foreign officials on his security clearance application.”

Aides to Kushner did not immediately respond to requests for comment on the letter from Cummings and the other Democrats on the Oversight Committee, which was accompanied by a demand for Kushner’s security clearance application and for “all documents and communications referring or relating to Mr. Kushner’s contacts or communications with Russian government officials or business representatives.” Cummings’ letter is the latest in a drumbeat of efforts by Democrats in Congress. More than 40 members wrote with similar concerns in May.

A White House spokesperson declined to comment.

As a senior adviser to Trump and as someone tasked with helping orchestrate Middle East peace talks, Kushner likely has access to highly sensitive intelligence. According to the letter, his top-secret clearance is temporary, pending a routine screening by the FBI.

The FBI has not identified Kushner as a target of its investigation into Russian meddling in the 2016 presidential election, recently taken over by special counsel Robert Mueller. Sources familiar with a parallel probe by the Senate Intelligence Committee, however, have confirmed to ABC News that Kushner’s previously undisclosed meetings with Russian officials have drawn the attention of its investigators. Senate investigators have requested documents from Kushner and are negotiating with him to arrange an interview. Through his attorney, Kushner has indicated his desire to cooperate with that probe.

The challenge to Kushner’s security clearance comes as the White House is facing questions about its decision to continue to allow retired Lt. Gen. Michael Flynn to access to the nation’s most carefully guarded secrets when he served as Trump’s national security adviser, even after Department of Justice officials warned that Flynn may have been susceptible to blackmail by Russian diplomats. The New York Times reported Wednesday that, for three weeks before he was fired, Flynn sat in on the most sensitive intelligence briefings in the White House.

He has denied anything improper occurred during his contacts with the Russian ambassador to the U.S., and sources close to Flynn have told ABC News they consider it ludicrous that anyone could have concluded he was vulnerable to blackmail.

Cummings, however, takes issue with the administration’s decision to continue allowing Flynn access to sensitive information after Justice Department lawyers notified the White House of their concerns.

“Concerns about Gen. Flynn’s false statements — as well as his concealment of communications with the Russian ambassador — raised obvious security concerns that should have resulted in an immediate suspension of his clearance while an investigation of the allegations proceeded,” Cummings wrote.

Kushner’s lawyer Jamie Gorelick, a deputy attorney general under Bill Clinton, said that on Jan. 18, Kushner filed an extensive security questionnaire known as the SF86, with an offer the next day to the FBI to provide omitted details of his Russian contacts during his background check interview by agents in person, The New York Times reported.

The SF86 requires applicants for security clearances to disclose — under criminal penalty for significant omissions — minute details of their life, including specific dates and purposes of foreign travel and any “close and/or continuing contact” with foreign nationals or receipt of foreign payments in the previous seven years.

The fact that Kushner received an interim security clearance despite failing to disclose all his contacts with the Russian ambassador and a Kremlin-owned bank is very unusual, according to one legal expert.

“It’s highly out of the ordinary for how it’s supposed to be done,” said Bradley Moss, a national security lawyer who handles cases involving intelligence community workers’ clearance problems.

Investigators conducting government background checks for those applying for top-secret clearances understand that people make mistakes on their SF86 disclosures and sometimes have to submit supplemental information, but Moss said he has never heard of an interim clearance being given to anyone who failed to disclose contacts with a foreign government.

“If Kushner’s clearance is still being adjudicated and there is this red flag of his failure to properly report numerous contacts with foreign government officials on his SF86, that would be major matter of concern, in terms of him being in charge of this mission to the Middle East,” Moss said.

Cummings and other House Democrats have no power to force the administration to rescind Kushner’s clearance. Trump has final word on who gets a security clearance when it comes to his staff, as the chief executive, by law, is the ultimate authority.