George W Bush and Barack Obama have both publicly criticised the political climate in the US, in what has been interpreted as a thinly-veiled attack on Donald Trump’s administration.

Neither of the former presidents named Mr Trump, but Mr Obama railed against the “politics of division”, and implied the Trump administration had set US democracy “back 50 years”, while Mr Bush criticised the “casual cruelty” and “bigotry”, which he said threatened American politics.

An unwritten rule in US politics is that former presidents maintain a silence over their successors, but Mr Bush and Mr Obama delivered an unprecedented twin blow to the White House on Thursday morning.

Speaking at a Democratic campaign rally in Newark, Mr Obama said: “Our politics is so divided and so angry and so nasty.”

“Instead of our politics reflecting our values, we’ve got politics infecting our communities. Instead of looking for ways of working together to get things done in a practical way, we’ve got folks who are deliberately trying to make folks angry, to demonise people who have different ideas… to provide a short-term tactical advantage.”

He added: “If you have to win a campaign by dividing people, you won’t be able to govern them.”

"What we can't have is the same old politics of division that we have seen so many times before, that dates back centuries."

Earlier in the morning, the last Republican before Mr Trump to occupy the White House, Mr Bush issued his own warning while speaking in New York.

Mr 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.”

He 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.”

Dr Jacob Parakilas, an expert in US foreign policy at Chatham House, told The Independent the move signals a new willingness on Mr Obama’s part to re-engage in the political discourse.

He said: “It’s not entirely unprecedented, but it is very rare for presidents to criticise their successors, it’s notable that neither Obama nor Bush called out Trump directly. I think they’re both still trying to give voice to criticisms without declaring war directly on Trump.”

He added: “What this represents is Obama beginning to move out of that framework and become a little bit more willing to reengage in the political debate.

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