US Interior Secretary Ryan Zinke, who has sought to open US offshore waters to oil and gas drilling despite environmental protests, will be leaving his post at the end of the year, US President Donald Trump tweeted today.

Mr Zinke is the latest high-profile departure from his administration.

Yesterday, Mr Trump said his budget chief, Mick Mulvaney, would take over as White House chief of staff on a temporary basis after former New Jersey Governor Chris Christie abruptly ruled himself out for the post.

Mr Trump did not give a reason for Mr Zinke's departure. However, the former Navy Seal and ex-congressman from Montana has faced multiple probes into his use of security details, chartered flights and a real estate deal.

"The Trump administration will be announcing the new secretary of the Interior next week," he added.

Mr Zinke has run the Interior Department overseeing America’s vast public lands since early 2017. He has pursued Mr Trump’s agenda to promote oil drilling and coal mining by expanding federal leasing, cutting royalty rates, and easing land protections.

Mr Zinke, 51, was among Mr Trump's most active cabinet members, cutting huge wilderness national monuments in Utah to a fraction of their size and proposing offshore oil drilling in the Arctic, Pacific and Atlantic.

He became a darling of the US energy and mining industries and a prime target for conservationists and environmental groups.

Critics also questioned Mr Zinke's ethics and some of his moves triggered government investigations.

Senate Democratic leader Chuck Schumer applauded Mr Zinke's departure in a tweet: "Ryan Zinke was one of the most toxic members of the cabinet in the way he treated our environment, our precious public lands, and the way he treated the govt like it was his personal honey pot."

"The swamp cabinet will be a little less foul without him," Mr Schumer said.

In July, the US Interior Department’s Office of Inspector General began investigating a Montana land deal between a foundation Mr Zinke set up and a development group backed by the chairman of oil service company Halliburton Co, which has business with the Interior Department.

In late October, that investigation was referred to the US Justice Department for a possible criminal investigation, according to multiple media reports. The Department of Justice and the Interior Department have declined to comment.

There are two other continuing investigations of Mr Zinke’s conduct. Interior’s watchdog is examining whether the department purposefully redrew the boundaries of Utah's Grand Staircase-Escalante National Monument in a way that would benefit a state lawmaker who owns adjoining property.

The watchdog is also investigating Mr Zinke's decision to block casinos proposed by two Connecticut Native American tribes. Critics allege he made that move, overruling his staff's recommendation, shortly after he met with lobbyists for MGM Resorts International, which owns a new casino in the region.

Mr Zinke has repeatedly denied any wrongdoing.