While the US is one of the richest nations, entrenched poverty already experienced by many will be made worse by policies promoted by Mr Trump and the Republicans, in particular a planned tax overhaul that critics say gives huge cuts to the wealthy, it added.
“The American dream is rapidly becoming the American illusion, as the United States now has the lowest rate of social mobility of any of the rich countries,” said Philip Alston the UN Nations Special Rapporteur on extreme poverty and human rights.
“American exceptionalism was a constant theme in my conversations. But instead of realising its founders’ admirable commitments, today’s United States has proved itself to be exceptional in far more problematic ways that are shockingly at odds with its immense wealth and its founding commitment to human rights.”
He added: “There is no other developed country where so many voters are disenfranchised and where so few poor voters even care to go to the polls.”
Mr Alston delivered his comments alongside a draft report which he made public. His final report will be available in the spring of 2018 and will be presented to the UN Human Rights Council in Geneva in June of next year.
On his 15-day visit around the US, the Australian Mr Alston, a law professor at New York University, visited Los Angeles, San Francisco, Alabama, Georgia, Puerto Rico and West Virginia. He spoke to low-income families and officials.
In Alabama, he saw conditions he said he had never previously witnessed in the developed world. Taken to Butler and then Lowndes counties he was shown families whose homes had no proper sewage system and who create their own unhygienic systems using PVC piping.
While E. coli is common in both communities, which are largely made up of African Americans, academics recently discovered that hookworm, a disease associated with extreme poverty and which was thought to have been eradicated in the US more than 100 years ago, still persists in pockets of Lowndes County, located just 20 miles from the state capital, Montgomery.
“I think it’s very uncommon in the first world. This is not a sight that one normally sees,” Mr Alston told AL.com as he visited Alabama. “I’d have to say that I haven’t seen this.”
Mr Alston said statistics from the US Census Bureau in September 2017 indicated more than 40m people - more than one in eight Americans - were living in poverty. Almost half of those, 18.5m, were living in deep poverty, with reported family income below half of the poverty threshold.
He said while it was frequently assumed that poor people belonged almost entirely to minority groups, but noted there were eight million more white people than African-Americans living in poverty. “The face of poverty in America is not only black or Hispanic, but also white, Asian and many other colours,” he said.
He said the tax and welfare reforms being proposed by Mr Trump and the Republican leadership in Congress, were likely to have “devastating consequences” for the poorest 20 per cent of Americans.
“The proposed tax reform package stakes out America’s bid to become the most unequal society in the world,” Mr Alston said.
“It will greatly increase the already high levels of wealth and income inequality between the richest one percent and the poorest 50 percent of Americans."
He added: “The dramatic cuts in welfare, foreshadowed by President Trump and Speaker Paul Ryan, and already beginning to be implemented by the administration, will essentially shred crucial dimensions of a safety net that is already full of holes.”
Republicans declined to meet Mr Alston in Washington, with the office of Speaker Paul Ryan saying he was too busy. Yet independent senator Bernie Sanders seized on the envoy’s findings.
He wrote on Twitter: “Our job: fight back against the reactionary Trump agenda and for a progressive agenda that works for the middle class, not the one per cent.”