US President Donald Trump arrived home from his one-on-one meeting with Vladimir Putin in Helsinki to a wave of criticism that has crossed party lines.

Mr Trump has been slammed for the comments he made at a press conference after the two leaders had met, in which he appeared to take the side of Mr Putin and Russia over his own FBI in regard to Russia’s alleged meddling in the 2016 presidential election.

Mr Trump resisted when asked to condemn Russian meddling in the election, and instead complained about a Democratic National Committee computer server and emails belonging to Hillary Clinton.

The fallout to the meeting and press conference has called the conduct of both Mr Trump and Mr Putin into question, with the Russian President again denying the Russian state had any part in influencing the US election – even as a Fox News journalist tried to hand him the indictment documents of 12 Russian intelligence officials during an interview.

Politicians from both major parties and former intelligence officials appeared shocked, dismayed and uneasy with Mr Trump’s suggestion he believes Mr Putin’s denial of interfering in the 2016 elections.

It was a remarkable break with US intelligence officials and the Justice Department and, just as alarming for some, Mr Trump also put the two countries on the same footing when casting blame for their strained relations.

Senator John McCain called it, “one of the most disgraceful performances by an American president in memory”, while Senator Ben Sasse called it “bizarre”.

Today’s press conference in #Helsinki was one of the most disgraceful performances by an American president in memory.

My full statement on the #HelsinkiSummit: https://t.co/lApjctZyZl

— John McCain (@SenJohnMcCain) July 16, 2018

Senator Jeff Flake called the press conference “shameful” and Senator Lindsey Graham tweeted that it was a “bad day for the US”.

“This was a very good day for President Putin,” said Senator Bob Corker, the chairman of the Foreign Relations Committee. He said Mr Trump’s refusal to condemn Russian interference in the 2016 election made the US, “look like a pushover”.

Republican Will Hurd said he had seen Russian intelligence manipulate many people in his earlier career as a CIA officer. But, he tweeted:

I've seen Russian intelligence manipulate many people over my professional career and I never would have thought that the US President would become one of the ones getting played by old KGB hands.

— Will Hurd (@WillHurd) July 16, 2018

House Speaker Paul Ryan weighed in to say there was “no question” Russia interfered in the 2016 presidential election and “no moral equivalence” between the US and Russia.

After meeting with the Russian President, Donald Trump faced a number of questions over the US probe into election interference. Here are the five key moments from their summit.

“The President must appreciate that Russia is not our ally,” Mr Ryan said in a statement.

[Russia] remains hostile to our most basic values and ideals.”

Much of the Republican rebuke came from politicians who have been willing to openly criticise the President, a group that remains a minority in the GOP.

Many top Republicans remained on the sidelines after the Justice Department on Friday indicted 12 Russian intelligence officials for election-related hacking.

But several Republicans who do not typically buck the President raised concerns, shocked by Monday’s performance.

Trump ally Newt Gingrich called it, “the most serious mistake” of Mr Trump’s presidency — and one that, “must be corrected immediately”.

Donald Trump and Vladimir Putin front the media before their summit. Photo: AAP

Democrats pleaded with their GOP colleagues who have majority control of Congress to rein in the President and become a stronger legislative check on the executive branch.

Senator Chuck Schumer, the minority leader, said never in the history of the country had an American president supported an adversary the way Mr Trump sided with Mr Putin.

He challenged Republicans to move beyond words and to confront the President directly by increasing sanctions on Russia and requesting testimony about the summit from Trump administration officials, among other things.

“We need our Republican colleagues to stand up for the good of this country,” he said.

Millions of Americans will continue to wonder if the only possible explanation for this dangerous behavior is the possibility that President Putin holds damaging information over President Trump.

— Chuck Schumer (@SenSchumer) July 16, 2018

And House Minority Leader Nancy Pelosi said Mr Trump’s weakness in front of Mr Putin was not just “embarrassing” but also, “proves that the Russians have something on the President, personally, financially or politically”.

Republicans have been hesitant to fully confront the President, who remains popular among GOP voters back home. But Mr Trump’s hold on the GOP is being put to the test by his willingness to align with Mr Putin, a leader whom Republicans routinely describe as an enemy of the United States.

-ABC