Omarosa Manigault (R), White House Director of Communications for the Office of Public Liaison, sits behind US President Donald Trump as he speaks during a meeting with teachers, school administrators and parents in the Roosevelt Room of the White House in Washington, DC, February 14, 2017. /

President Donald Trump's 2016 campaign paid most of the women who worked for it — including notorious "The Apprentice" contestant Omarosa Manigault Newman — 20% less than their male counterparts, a court filing said Monday.

The filing, part of a lawsuit against Trump, says that an analysis has found that other than a "small handful of employees in senior leadership roles," female workers on the campaign were paid on average $3,865 per month and "males were paid $4,568 — a stunning gap of 18.2 percent."

The campaign "maintained a common policy ... of paying female employees less than their male counterparts for the same or similar work," says the filing by Alva Johnson, a former Trump campaign worker.

In Johnson's suit filed earlier this year in federal court in Tampa, Florida, she alleged that Trump kissed her without her consent at a campaign rally in August 2016.

Johnson, who is black, in her suit alleges gender and race discrimination, claiming she was paid less than white or male colleagues even though she excelled at her job of organizing volunteers and planning rallies.

The White House has said Johnson's claim of Trump kissing her is false and contradicted by several eyewitnesses.

Neither the Trump campaign nor a lawyer for the president and his reelection effort immediately responded to CNBC's request for comment Monday on Johnson's new filing and the analysis of pay and gender.

Johnson is asking to be named the lead plaintiff for a collective action by other women who were paid less by the Trump campaign than male workers. Her suit says that she was paid $3,000 per month from January to August 2016 and $4,000 per month from September 2016 until she left the campaign, which was "considerably less than that paid to male Campaign staff who had the same responsibilities as she did and lower even than male Campaign staff who had fewer responsibilities than she did."

The analysis of pay by the Trump campaign, which was conducted by economist Phillip Johnson, was used to bolster her bid. In her filing Monday, Alva Johnson asked a judge to require that Trump's campaign identify all potential members of a proposed collective action.

"This case is about two things: Donald Trump's predation, and his campaign's discrimination against women and people of color," said Johnson's attorney, Hassan Zavareei.

On Monday, Manigault Newman, a black woman who is a former White House advisor and who worked on Trump's campaign as director of African American outreach, submitted a declaration in Johnson's case backing her effort.

"I believe that Donald J. Trump for President Inc. paid me and other similarly situated female employees less than male employees who performed the same or similar job duties under similar working conditions," Manigault Newman wrote in her filing.

She added that one of the campaign's spokesmen, Bryan Lanza, "whose work required substantially equal skill, effort, and responsibility as mine was paid more than me despite being similarly situated."

Lanza did not immediately return a request for comment from CNBC.

In a statement to the media, Manigault Newman said, "This filing is about examining the gender pay gap in the Trump/Pence campaign. The gender pay gap exists between what men and women were paid during Donald Trump's first presidential campaign. It also discriminates against minorities."

"While I strongly suspected I was subjected to pay discrimination while with the Trump Campaign, I have since seen expert analysis confirming this to be true. The numbers don't lie," she said.

"After nearly 20 years inside the Beltway, working for two White Houses and countless political campaigns, I've never witnessed such egregious violations as I did during my time under the leadership of Donald Trump and Mike Pence. I am joining this effort for women and minorities to help level the playing field in the political arena between men and women."

"It is time for all of us to blow the whistle on the wrongdoings of this Campaign."

Manigault Newman, who at one time was a fierce defender of Trump's, became infamous as a breakout star on Trump's former reality show, "The Apprentice."

After Trump won the election, Manigault Newman was selected to work on Trump's presidential transition team and became a member of the president's communications staff after his inauguration. She resigned from the White House in late 2017.

Less than a year later, Manigault Newman released her book "Unhinged," a highly critical tell-all about her time in Trump's orbit. In it, she accused Trump of being a "racist" and said that tapes existed of Trump saying the "N" word while filming "The Apprentice." But she also said she never personally had heard Trump use that word.

The White House said in response that the book was "riddled with lies and false accusations."