Kamala Harris' chief of staff has shut out some of the vice president's longtime political and business world allies as the current administration struggles with several challenges, including voting rights and the border crisis, a report said.

Some people familiar with the matter told CNBC that Kamala Harris has not been returning phone calls to people who have considered themselves members of her inner circle, which includes donors and people who supported her run on the Senate and the White House.

Kamala Harris regularly speaks with President Joe Biden, her family members, a tight group of friends, including her strategists, under her chief of staff Tina Flournoy's watch, the sources said.

Tina Flournoy had earned a tough reputation while working for former President Bill Clinton. The sources noted that Tina Flournoy exerts her power as a gatekeeper to the vice president.

And because of this, the source told CNBC that some of Kamala Harris' allies working outside the federal government are "struggling to get their calls returned after years of regularly being in touch with the vice president."

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Tina Flournoy's Gatekeeping

A person familiar with Tina Flournoy's interactions also told CNBC that she sometimes directly asks people what they want from the vice president.

If a person expresses that they would like to have a brief talk with Kamala Harris, she reportedly told them that they could speak with the vice president "at future private events." 

And if it is about where Kamala Harris stands on policy, Flournoy would say they cannot speak to the vice president about policy or introduce them to one of her policy advisors, Business Insider reported. The sources also told CNBC that many of the advisors' and donors' calls have yet to be returned.

One of Kamala Harris' allies said they have accepted that the vice president is simply in a higher-level role. They have also been in contact with Flournoy.

The ally told CNBC that Tina Flournoy is a strong chief of staff, and there is no question that she is very focused on making sure that the vice president can focus on issues on hand, such as voting rights, vaccination efforts, and the current border crisis.

Tina Flournoy Picked as Kamala Harris' Chief of Staff 

Kamala Harris had picked Tina Flournoy to be her chief of staff last December. Her appointment to the veteran Democratic strategist adds to a team of advisers led by Black women.

Flournoy's working style for Kamala Harris is familiar to people who knew her while working for Clinton, who had praised the hiring of Flournoy after Harris made the official announcement. Flournoy had taken over the managing access to Clinton after his long-time right-hand, Doug Band, left. 

Band co-founded the corporate consulting firm Teneo, which is known for helping Clinton's post-presidential life. It includes assisting in launching the foundation and the Clinton Global Initiative.

Clinton and Band had engaged with some controversial celebrities and executives, including the known sex predator Jeffrey Epstein, Vanity Fair reported.

Tina Flournoy's Background

Tina Flournoy has deep connections in Washington D.C. She worked as a law clerk for Julia Cooper Mack, who is a judge on the D.C. Court of Appeals. She then jumped and started her stint as a counsel for the Democratic National Convention.

Flournoy is listed as general counsel for cigarette maker Phillip Morris in a 1995 White House press advisory. She also served as traveling chief of staff for Sen. Joe Lieberman during the 2000 presidential campaign.

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WATCH: VP-Elect Harris Picks Savannah Native Tina Flournoy as Chief of Staff - From WSAV 3