The former presidents Barack Obama and George W Bush have separately expressed concern about the current political climate in the US, in comments seen as warnings about Donald Trump.

With neither mentioning the current President by name, Obama urged Americans to reject the politics of 'division' and 'fear', while Bush criticised 'bullying and prejudice' in public life.

Addressing a Democratic campaign event in Newark, New Jersey, Obama said that Americans should 'send a message to the world that we are rejecting a politics of division, we are rejecting a politics of fear'.

Trump's immediate predecessor added: 'What we can't have is the same old politics of division that we have seen so many times before that dates back centuries. Some of the politics we see now, we thought we put that to bed. That's folks looking 50 years back. It's the 21st century, not the 19th century. Come on!'

Speaking later in Richmond, Virginia, Obama echoed this theme, saying: 'We've got folks who are deliberately trying to make folks angry, to demonise people who have different ideas, to get the base all riled up because it provides a short-term tactical advantage.'

Also speaking last night in New York, Bush said: 'Bigotry seems emboldened. Our politics seems more vulnerable to conspiracy theories and outright fabrication.

'There are some signs that the intensity of support for democracy itself has waned – especially among the young.'

Americans, he said, have 'seen our discourse degraded by casual cruelty'.

And speaking up for immigration, the former Republican president added: 'At times it can seem like the forces pulling us apart are stronger than the forces binding us together. We've seen nationalism distorted into nativism, forgotten the dynamism that immigration has always brought to America.'

During last year's presidential contest, Trump attacked both former presidents, but he has so far yet to respond to last night's comments.