Newt Gingrich. AP Photo/Efrem Lukatsky Former House Speaker Newt Gingrich, one of President Donald Trump's top allies, went after special counsel Robert Mueller in a Thursday morning tweetstorm, calling the former FBI director "the tip of the deep state spear aimed at" Trump.

Gingrich posted his tweets after The Washington Post reported Wednesday night that Mueller's investigation into Russian interference in the 2016 election and whether the Trump campaign colluded with Russian officials now expanded to include a probe into whether Trump committed obstruction of justice with his firing of former FBI Director James Comey last month.

Mueller is also seeking proof of whether Trump associates committed financial crimes.

"Should now be clear Mueller is the 'anti-Trump special counsel,'" Gingrich tweeted.

The former House speaker wrote that Mueller "is setting up a dragnet of obstruction, financial questions and every aspect of Trump's life and his associates lives."

"Very dangerous," he wrote, saying it's clear following the Post's story that Mueller is "the tip of the deep state spear aimed at destroying or at a minimum undermining and crippling the Trump presidency."

"The brazen redefinition of Mueller's task tells you how arrogant the deep state is and how confident it is it can get away with anything," he added.

Gingrich's posts came as Trump himself blasted out tweets on the Post's story.

"They made up a phony collusion with the Russians story, found zero proof, so now they go for obstruction of justice on the phony story," he wrote. "Nice."

Trump added that the investigation was "the single greatest WITCH HUNT" in US political history and is being led "by some very bad and conflicted people!"

Gingrich's tweets marked a coming of full circle in an effort by some of Trump's most prominent allies to delegitimize the Mueller-led investigation.

Following Comey's testimony last week, when he alluded to the Mueller investigation that already likely included a probe into obstruction of justice, a number of Trump's top conservative boosters began pointing out flaws they saw in Mueller and his investigation.

Many of those supporters took issue with Mueller hiring top attorneys, whom they say are partisan, to assist with his investigation. Those same Trump supporters also took issue with Comey's relationship with Mueller, which they say is too close.

The most prominent of those Trump backers was Gingrich, who tweeted Monday that Republicans were "delusional" if they thought Mueller would be fair. When Mueller was first hired by Deputy Attorney General Rod Rosenstein in mid-May, after the initial firestorm surrounding Trump's abrupt firing of Comey, Gingrich expressed support, tweeting that Mueller's "reputation is impeccable for honesty and integrity."

While the White House denied that Trump had any intention to fire Mueller, the New York Times reported Tuesday night that the president had begun entertaining the idea of firing Mueller last month.

The reports that Trump was considering ousting Mueller appeared to lead to officials leaking to the Post that the Mueller investigation included probing possible obstruction of justice, a move that would make it more difficult for Trump to remove Mueller without increased backlash.