European newspapers have expressed horror at the prospect of Boris Johnson becoming the UK’s next prime minister, describing him as a scandal-proof serial promise-breaker whose arrival at No 10 would be “a calamity for his country and for Europe”.

Le Monde, in an excoriating editorial, said Johnson had shown himself to be “a stranger to logic and convictions” in a career rich in “deceits, blunders and failures”. In the run-up to the 2016 referendum he “told lies on the side of a bus, promised the UK could have its cake and eat it, and compared the EU to the Third Reich,” it said.

As foreign secretary he “made his country an object of ridicule around the world with his amateurism, flippancy and ignorance”, France’s newspaper of record continued. Rivalling Nigel Farage for populism, Johnson’s “jingoistic rhetoric” promised Britons an unrealistic “glorious global future”.

His threat to withhold the €39bn Brexit divorce settlement would have “incalculable consequences”, damaging the international credibility of a country priding itself on being a champion of the rule of law, Le Monde said. And for the EU a Johnson premiership would mean “a mini-Trump across the Channel, dedicated to its sabotage”. Britain would become “a hostile principality, built on social, fiscal and environmental deregulation.”

The Dutch daily newspaper de Volkskrant said Johnson’s appeal was as a “Brexit-believer, a 21st-century buccaneer, a pirate who surfs the oceans in search of wealth, unconstrained by rules or conventions”. But it said there was good reason to think he “believes rather more in himself than in Brexit”.

It said Johnson’s main strength was that “no scandal seems to stick, be it extramarital affairs, fraudulent statements, offensive utterances or an offer to help an old college friend attack a tabloid journalist.” For the Tories he was “the joker in the card game that Brexit has become”.

Germany’s Handelsblatt said Johnson would be “fatal for Britain”. If he succeeded Theresa May at the end of July, “the UK and the international partners of the fifth largest economy in the world are likely to encounter chaos”.

It said Johnson “has never shied away from making bold promises, few of which he has ever kept”. All the signs were that he would continue in this vein, it added, if only because “his sole chance of becoming prime minister is if he meets the expectations of the Brexit hardliners”.

Handelsblatt predicted that in the battle for the Tory leadership, Johnson “will promise a lot – and ultimately prove unable to deliver … It is to be hoped that he will be beaten in the race for the premiership. Unfortunately, given Britain’s current pro-Brexit mood, he may not be.”

Spain’s El País cautioned that “the only person capable of defeating Boris Johnson – and there are precedents – is Boris Johnson himself”. The paper said Conservative Eurosceptics had plainly decided to “ignore the many doubts raised by the unpredictable personality of the former mayor of London”.

Johnson’s campaign was “very calculated, with minimal media appearances and an attempt to convey the seriousness and rigour he has lacked in recent years”, it said, and he appeared “much more focused and determined than three years ago”. But he may not be able to dodge his “past mistakes and gaffes” so easily.

In Italy, Corriere della Sera published an interview with the veteran Tory politician Chris Patten, who described the favourite to become Britain’s next prime minister as “Trump’s poodle: a liar who does not pay attention to the detail of reality, tells people what they want to hear and relies on their ignorance”.

Patten said Johnson exemplified the “collapse of rationality, of the relationship between the facts and what we believe” in present-day politics. “What he is offering is impossible.”

• This article was amended on 13 June 2019. An earlier version referred to “a coruscating editorial” in Le Monde. This has been changed to “excoriating” to accord with our style guide.