Republican senator John McCain said on Friday Donald Trump’s administration was in “disarray” and that Nato’s founders would be alarmed by the growing unwillingness to “separate truth from lies”.

The Republican Senator broke with the reassuring message that US officials visiting Germany have sought to convey on their debut trip to Europe, telling a Munich security conference the resignation of the new president’s security adviser, Michael Flynn, over his contacts with Russia reflected deep problems in Washington.

“I think that the Flynn issue obviously is something that shows that in many respects this administration is in disarray and they’ve got a lot of work to do,” said Mr McCain, a known Trump critic, even as he praised Mr Trump’s defence secretary.

“The president, I think, makes statements [and] other occasions contradicts himself. So we’ve learned to watch what the president does as opposed to what he says,” he said.

Without mentioning the president’s name, Mr McCain lamented a shift in the US and Europe away from the “universal values” that forged the Nato alliance seven decades ago.

Mr McCain also said the alliance’s founders would be “alarmed by the growing inability, and even unwillingness, to separate truth from lies.”

The chairman of the Armed Services Committee, said “more and more of our fellow citizens seem to be flirting with authoritarianism and romanticising it as our moral equivalent”. The senator also regretted the “hardening resentment we see toward immigrants, and refugees, and minority groups, especially Muslims”.

European governments have been unsettled by the signals sent by Trump on a range of foreign policy issues ranging from Nato and Russia to Iran, Israel and European integration.

The debut trip to Europe of Trump’s defence secretary, Jim Mattis, and his secretary of state, Rex Tillerson, to a meeting of G20 counterparts in Bonn, went some way to assuaging concerns as they both took a more traditional US position.

But Mr Trump is wrestling with a growing controversy at home about potential ties between his aides and Russia, which he dismissed on Thursday as a “ruse” and “scam” perpetrated by a hostile news media.

Nato

Mr Mattis made clear to allies, both at Nato in Brussels and in Munich, that the US would not retreat from leadership as the European continent grapples with an assertive Russia, wars in eastern and southern Mediterranean countries and attacks by Islamist militants.

US vice-president Mike Pence will address the Munich conference on Saturday with a similar message of reassurance. Pence will say Europe is an “indispensable partner”, a senior White House foreign policy adviser told reporters.

Mr Mattis told a crowd that included heads of state and more than 70 defence ministers that Trump backed Nato. “President Trump came into office and has thrown now his full support to Nato. He too espouses Nato’s need to adapt to today’s strategic situation for it to remain credible, capable and relevant,” Mr Mattis said.

Mr Mattis said the US and its European allies had a shared understanding of the challenges ahead. Trump has alarmed allies by expressing admiration for Russian president Vladimir Putin.

Mr Mattis, however, has spoken out strongly against Russia while in Europe. After talks with Nato allies in Brussels on Thursday, he said he did not believe it would be possible to collaborate militarily with Moscow, at least for now.

The Europeans may need more convincing that Washington stands with it on a range of security issues. “There is still a lot of uncertainty,” Sebastian Kurz, Austria’s foreign minister, told reporters. “The big topic in Munich is looking to the USA to see which developments to expect next.”

European intelligence agencies have warned that Russia is also seeking to destabilise governments and influence elections across Europe with cyber attacks, fake news and propaganda and by funding far-right political parties.

British defence minister Michael Fallon said: “We should be under no illusions about the step-change in Russian behaviour over the last couple of years, even after Crimea”, referring to Moscow’s 2014 annexation of the Ukrainian peninsula.

“We have seen a step-change in Russian military aggression, but also in propaganda, in misinformation and a succession of persistent attacks on western democracies, interference in a whole series of elections including ... the United States. ”

Nato’s secretary-general, Jens Stoltenberg, held talks with Russian foreign minister Sergei Lavrov in Munich, seeing progress on encouraging Moscow to be more open about its military exercises that the alliance says are unpredictable.

Russia says it is the western alliance, not Moscow, that is destabilising Europe by sending troops to its western borders. “We have different views,” Mr Stoltenberg said of the crisis in Ukraine, where the west accuses the Kremlin of arming separatist rebels in a conflict that has killed 10,000 people since April 2014. Russia says the conflict is a civil war.

Agencies and Guardian