Former White House counsel Don McGahn raised concerns about the security clearance of the president's son-in-law and senior adviser, Jared Kushner, in a memo to then-White House chief of staff John Kelly in early 2018, according to a new book.

In the upcoming book from New York Times correspondent Michael Schmidt, "Donald Trump v. The United States," Schmidt unveils a previously unreported two-page memo in which McGahn reportedly warns Kelly that Kushner should not receive a top-level security clearance unless "serious additional concerns" raised by Kushner's FBI background check were resolved, Axios reported Sunday.

"The information you were briefed on one week ago and subsequently relayed to me, raises serious additional concerns about whether this individual ought to retain a top security clearance until such issues can be investigated and resolved," the memo reportedly stated.

"Interim secret is the highest clearance that I can concur until further information is received," it reportedly continued.

The memo is the most direct evidence yet reported pointing to significant security issues raised during Kushner's FBI background check; it had previously been reported that McGahn's office had recommended against Kushner receiving a top-secret clearance and that Kelly had authored a memo noting at the time that he had been "ordered" by President Trump to override that recommendation and grant the clearance to Kushner anyway.

Representatives for Kushner maintained at the time that the White House had conveyed to Kushner that his clearance application had been handled under normal protocols without pressure from any officials.

“In 2018, White House and security clearance officials affirmed that Mr. Kushner’s security clearance was handled in the regular process with no pressure from anyone," a spokesman for Kushner said in 2018.