Rep. Duncan Hunter, R-Calif., left, is calling for Navy Secretary Ray Mabus to resign after Mabus criticized the Marine Corps' study of gender integration of ground combat units. speaks during a news conference on Capitol Hill, Thursday, April 7, 2011, in Washington. (AP Photo/Carolyn Kaster and by Jason Davis/Getty Images)

Congressman Duncan Hunter, left, a California Republican and Marine Corps combat veteran, is calling for Navy Secretary Ray Mabus to resign after Mabus criticized the Marine Corps’ gender integration research. (Photos by Carolyn Kaster/AP and by Jason Davis/Getty Images)

An outspoken member of the House Armed Services Committee on Thursday called for Navy Secretary Ray Mabus to resign, the latest twist in what has become an impassioned public feud over the pending decision whether to let women join the Marine Corps infantry and its elite special operations command.

In a letter to Defense Secretary Ash Carter, California Congressman Duncan Hunter, a Marine Corps combat veteran, slammed the secretary over his recent criticism of a Marine Corps research project that concluded combat teams containing women were less effective than those composed entirely of men.

READ: Congressman Duncan Hunter’s letter to Defense Secretary Ash Carter

“Recent statements by Secretary of the Navy Ray Mabus — openly criticizing the Marine Corps and its study on the impact of gender integration — have created a deep sense of concern for the ability of the Navy Secretary to be objective and to continue leading the Marine Corps,” Hunter wrote to Carter.

RELATED: Congressman says SecNav’s stance on women in combat insults Marines

A spokesman for Mabus declined to discuss Hunter’s letter. The secretary has said previously that he believes all ground combat jobs should be open to women who can meet rigorous gender-neutral physical standards.

Also on Thursday, the powerful head of the Senate Armed Services Committee, Sen. John McCain, told the Washington Examiner that if Mabus was dissatisfied with the Marine Corps’ study then he should have halted it months ago. Separately, members of the House Armed Services Committee have asked for a briefing on the Marine Corps’ gender research findings, according to a Thursday report by The Hill.

The military is on the cusp of historic change, with a mandate to open all combat roles to women by January. Each of the services has until Oct. 1 to request any exemptions to that policy.

Mabus has made his intentions clear, saying he won’t allow either the Navy or the Marine Corps to keep any specialties closed to women.

“That’s still my call,” he told Navy Times in an exclusive interview Sept. 1. “I do not see a reason for an exemption.”

Days later, Mabus went a step further, telling NPR that the Marine Corps’ study was flawed. He reiterated his position again this week during a speaking engagement in Ohio.

RELATED: Mabus: I’m not asking for women-in-combat exemptions

Conducted over nine months, the Marine Corps’ study involved about 400 Marines, including approximately 100 women. Men and women were assigned to infantry and other ground combat roles as part of the research. They began the experiment in North Carolina and then moved to California, undertaking intensive training in the desert and mountains.

Marine officials concluded that women were injured more often than men, fired their weapons with less accuracy and experienced greater difficulty when tasked with evacuating simulated casualties. Mabus, however, contends the female volunteers were perhaps not the strongest that the Marine Corps could have put forward.

Mabus also has suggested the study’s results were predetermined.

“It started out with a fairly large component of the men thinking ‘this is not a good idea,’ and ‘women will never be able to do this,’ ” Mabus told NPR in an interview broadcast on Sept. 11. “When you start out with that mindset, you’re almost presupposing the outcome.”

Those remarks incited outrage within the Marine Corps, with one combat decorated senior enlisted leader taking to Facebook to call Mabus’ remarks insulting and uninformed.

RELATED: Marine war hero: SecNav ‘way off base’ on women in combat

In his letter to Carter, Hunter called Mabus biased, criticizing the secretary for declaring his decision before being briefed on the Marine Corps’ findings. At a minimum, Hunter said, Mabus should be sidelined from this decision-making process.

“He has openly disrespected the Marine Corps as an institution, and he insulted the competency of Marines by disregarding their professional judgment, their combat experience and their quality of leadership,” Hunter wrote. “Such a significant loss of respect is detrimental to the ability of the Navy Secretary to effectively lead the men and women of the Marine Corps and ensure the service maintains the highest level of combat effectiveness.”

Staff writer David Larter co-authored this report.