Gingrich Turns on Longtime Friend Trump Over Putin Comments: It's the 'Most Serious Mistake of His Presidency'

President Donald Trump appears to have upset even his closest allies with comments at a joint press conference alongside Russian President Vladimir Putin in Helsinki. Newt Gingrich has described it as "the most serious mistake" of Trump's presidency.

The former House speaker, and the president's long-time confidante, was quick to criticize the president's appearance alongside Putin on Monday, which saw Trump suggest he believed Putin's denials on alleged election meddling by Russia.

"President Trump must clarify his statements in Helsinki on our intelligence system and Putin," Gingrich wrote in a tweet on Monday.

"It is the most serious mistake of his presidency and must be corrected—immediately," he added.

The president saw an immediate reaction from both Democrats and Republicans following his press conference with Putin, when he spoke with reporters and suggested he believed the Russian leader's denial of election meddling over his own intelligence community's opinion.

"They say it's Russia. I have President Putin. He just said it's not Russia," Trump told reporters following his press conference with Putin.

"I will say this: I don't see any reason why it would be… I have great confidence in my intelligence people, but I will tell you that President Putin was extremely strong and powerful in his denial today," he added.

Gingrich is not alone in his criticism of the president's actions during the Helsinki summit with the Russian leader, with Senator John McCain, House Speaker Paul Ryan, and a number of Democratic lawmakers also voicing their concern about the comments. However, Gingrich is usually reluctant to criticize his friend.

Trump himself was quick to respond to criticism, tweeting from Air Force One: "As I said today and many times before, "I have GREAT confidence in MY intelligence people." However, I also recognize that in order to build a brighter future, we cannot exclusively focus on the past – as the world's two largest nuclear powers, we must get along! ‪#HELSINKI2018."

Despite his longstanding defense of Trump, it is not the first time Gingrich has made it known that he doesn't agree with everything the president does. In April, the Republican suggested Trump had mishandled the memo from Deputy Attorney General Rod Rosenstein on the firing of FBI chief James Comey.

"First of all, I urge everybody to read the original Rosenstein memo about Comey, which Trump totally mishandled," Gingrich said on Fox News Sunday in April.

"What Trump should have done is released that memo in a state of shock. Let the country, through Sunday talk shows, deal with the memo. It's devastating. It's clear that if you got that memo and you're the president, you would have fired Comey," he added.

The White House did not immediately respond to a request for comment.