Jim DeMint has resigned as leader of the conservative Heritage Foundation think tank, the group’s board of trustees announced Tuesday -- confirming widespread reports that the former South Carolina GOP senator was being removed.

Chairman Thomas A. Saunders III said the board requested DeMint’s resignation by unanimous vote and has elected Heritage founder Ed Feulner as interim president and chief executive officer.

READ THE STATEMENT

In a blistering, roughly 500-word statement, Saunders said the decision followed a “comprehensive and independent review” of the entire organization and that the board had found “significant and worsening management issues that led to a breakdown of internal communications and cooperation.

“While the organization has seen many successes, Jim DeMint and a handful of his closest advisers failed to resolve these problems,” Saunders concluded. “This was a difficult and necessary decision for the board to take.”

Reports that DeMint, a former House member and senator, was out surfaced late Friday. Heritage previously declined to comment on the issue, amid widespread speculation about what led to his departure.

DeMint, who took over the organization in January 2013, responded late Tuesday with a statement of his own that called Saunders' claims "puzzling."

"The board of trustees has praised our work for four years and approved performance bonuses for the entire management team each year for a job well done," DeMint said, adding that he was "proud to have been part of leading Heritage's most successful impact on a presidential transition team since the days of Ronald Reagan, culminating in the confirmation of Judge Gorsuch [to the Supreme Court] and one of the best presidential cabinets in recent history."

Sources told Fox News before the announcement that DeMint and those he had brought to Heritage from Capitol Hill mismanaged the roughly 44-year-old operation.

Other sources said Monday that calls for DeMint’s departure were driven by Michael Needham, chief executive of Heritage’s political advocacy group, Heritage Action for America.

Needham complained to the board that the foundation under DeMint was becoming too political with its outreach and messaging -- not on its founding mission of crafting conservative policy -- especially when Heritage Action was created in 2010 for such purposes, the sources said.

Needham declined to discuss the matter on “Fox News Sunday” but praised DeMint as a “patriot.”

DeMint’s annual salary at the time of his departure was estimated at $1 million-plus, with his contract ending in December.

In recent weeks, Heritage helped deliver a major victory for conservatives by getting Judge Neil Gorsuch nominated, then appointed to the Supreme Court.

However, the group under DeMint has also been criticized for getting too close to the populist-styled President Trump and his administration.

Heritage has also been blamed for thwarting the recent congressional effort to dismantle ObamaCare by demanding a full repeal of the 2010 health care law.

Ending the law would have been a big, long-sought victory for fiscal conservatives and fulfilled a major Trump campaign promise.

“Heritage is a permanent policy research institution fighting for conservative ideas,” Saunders said. “We remain committed … to the principles that have made America great: free enterprise; limited government; individual freedom; traditional American values; and a strong national defense.”

The 65-year-old DeMint is considered a founding member of the roughly 8-year-old Tea Party movement, which helped Republicans take the House in 2010, then continued to back challengers in GOP primaries in which incumbents were considered not conservative enough.

Republican Sens. Rand Paul ofKentucky; Mike Lee of Utah, and Ted Cruz ofTexas; are among those the movement helped get elected.

They were among 47 congressional Republicans who earlier this week signed a letter of support and thanks to DeMint.

DeMint came to Washington in 1999 as House member and was elected to the Senate 2013. He resigned from the Senate in 2013 to run the foundation.