President Trump has ordered a reduction in size of the National Security Council after a whistleblower complaint led to an impeachment inquiry.

The decision to make staff cuts, which will take place as officials complete their assignments and return to their home agencies, was conveyed last week by acting White House chief of staff Mick Mulvaney and new national security adviser Robert O’Brien this week, according to Bloomberg.

There are roughly 310 members of the forum meant to advise the president on foreign policy and national security matters. It is comprised of career government officials from the State Department, Pentagon, and intelligence agencies.

The move comes after it was reported that a CIA official, who was at one point assigned to the White House, filed a whistleblower complaint that raised concerns about Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky and an effort to conceal details of that private conversation and others using a highly secure computer system.

O'Brien took over as head of the National Security Council following last month's ouster of John Bolton, who has since slammed Trump's foreign policy on a number of fronts. He is also shopping around for a book deal and is said to have "a lot to dish."

Leaks from within the National Security Council were said to have been an issue under Bolton, who reportedly fought with Trump to release $400 million in military aid to Ukraine that the administration withheld until last month.

According to the complaint and notes of the July 25 call, Trump pressed Zelensky to work with his personal attorney Rudy Giuliani and Attorney General William Barr to investigate allegations of collusion between Democrats and Ukraine during the 2016 election and also Joe Biden, now a candidate for president, and his son Hunter Biden, who did business in Ukraine while his father was vice president.