These are people who've been fired or resigned from Trump's White House

U.S. President Donald Trump's White House has had the highest turnover of senior-level staff of the past five presidents, according to figures compiled by the Brookings Institution think-tank.

And the number of those leaving the West Wing may still grow.

Here are some senior figures who have been fired or quit the administration since Trump took office on Jan. 20, 2017.

2019

Randolph Alles - Director of the Secret Service Randolph "Tex" Alles insists he wasn't fired, but that his departure from his role was part of an "orderly transition in leadership" across the Department of Homeland Secretary. The announcement on April 8 came a day after the resignation of Homeland Security Secretary Kirstjen Nielsen, to whom Alles reports.

The Secret Service, responsible for protecting senior U.S. officials including the president and vice-president, had come under scrutiny after a Chinese woman carrying electronic devices was charged with bluffing her way through security checks at Trump's Mar-a-Lago resort in Florida.

Kirstjen Nielsen - U.S. Homeland Security Secretary Kirstjen Nielsen, who became best known for defending Trump's policy of separating migrant children from their parents, resigned on April 7. Repeatedly subjected to tough questioning by Democrats at congressional hearings, Nielsen became a lightning rod for criticism of Trump's policies. She was even confronted by protesters last year at a Mexican restaurant in Washington.

2018

James Mattis - Perhaps the most respected foreign policy official in Trump's administration, James Mattis announced his resignation on Dec. 20, a after day the president decided to pull the U.S. military out of Syria — a decision that was made without consulting with American allies and upended American policy in the region. In his resignation letter, Mattis told Trump he has "the right to have a secretary of defence whose views are better aligned with yours." Mattis was originally slated to remain in his role until February, but Trump quickly decided to accelerate the general departure's after the fallout from his resignation. Deputy Defence Secretary Patrick Shanahan took over Mattis's role on Jan. 1.

Ryan Zinke - U.S. Interior Secretary Ryan Zinke — in the face of federal investigations into his travel, political activity and potential conflicts of interest — left the Trump administration at the end of 2018. Trump nominated David Bernhardt, a former energy lobbyist and the acting secretary of the interior, as Zinke's replacement.

John Kelly - Trump said that White House chief of staff John Kelly also left his job at the end of the year. Kelly, a retired Marine Corps general, was hired to bring order to the chaotic Trump White House but ultimately fell out with his boss.

Jeff Sessions - After months of being attacked and ridiculed by the president, the former senator was forced out on Nov. 7.

Nikki Haley - She said on Oct. 9 that she would step down at the end of the year as U.S. ambassador to the United Nations. Trump put forward State Department spokesperson Heather Nauert as her successor, also subject to Senate review. Nauert subsequently withdrew her nomination, saying the two months since she was announced as Trump's latest pick for UN ambassador were "gruelling on my family."

Don McGahn - Trump said in August the White House counsel would leave amid strains between the two over the Mueller probe.

Scott Pruitt - The Environmental Protection Agency chief quit on July 5 under fire over a series of ethics controversies.

David Shulkin - White House officials said on March 28 that the Veteran Affairs secretary would resign.

H.R. McMaster - The national security adviser was replaced on March 22 with John Bolton.

Andrew McCabe - The deputy FBI director was fired in mid-March by Sessions.

Rex Tillerson - The secretary of state was fired by Trump on March 13 after rifts between them. On Friday, Trump tweeted that Tillerson was "dumb as a rock" and "lazy as hell."

Gary Cohn - The National Economic Council director and former Goldman Sachs president said on March 5 he would resign.

Hope Hicks - The White House communications director, a long-serving and trusted Trump aide, resigned on Feb. 28.

Rob Porter - The White House staff secretary resigned in February after accusations of domestic abuse from former wives.

2017

Omarosa Manigault Newman - The former reality TV star was fired as assistant to the president in December.

Richard Cordray - The U.S. Consumer Financial Protection Bureau's first director quit in November.

Tom Price - The Health and Human Services secretary quit under pressure from Trump on Sept. 29 over travel practices.

Stephen Bannon - Trump's chief strategist was fired by Trump in mid-August after clashing with White House moderates.

Anthony Scaramucci - The White House communications director was fired by Trump in July after 10 days on the job.

Reince Priebus - Replaced as chief of staff by John Kelly, Priebus lost Trump's confidence after setbacks in Congress.

Sean Spicer - Resigned as White House press secretary in July, ending a turbulent tenure.

Walter Shaub - The head of the U.S. Office of Government Ethics, who clashed with Trump, stepped down in July.

Michael Dubke - Resigned as White House communications director in late May.

James Comey - The FBI director, who led the Russia probe before Mueller, was fired by Trump in May.

Katie Walsh - The deputy White House chief of staff was transferred out to a Republican activist group in March.

Michael Flynn - Resigned in February as Trump's national security adviser. Flynn later pleaded guilty to lying to the FBI.

Sally Yates - Trump fired the acting U.S. attorney general in January after she ordered Justice Department lawyers not to enforce Trump's immigration ban.