David Frum, who is a senior ditor of The Atlantic magazine, wrote on Twitter that Mr Trump was the “worst human being ever to enter the presidency”.
Mr Frum worked for Mr Bush from 2000 to 2002 and also added that Andrew Jackson, the seventh President of the United States who was also considered a populist, “was at least physically brave”.
Mr Frum tweeted: "The worst human being ever to enter the presidency, and I include all the slaveholders."
Mr Trump was sworn in as the 45th President of the United States and said this signalled the start of power being transferred from Washington to “the people”.
“We the citizens of America are now joined in a great national effort to rebuild our country and restore its promise for all of our people,” Mr Trump said.
Disorder broke out in Washington during the inauguration as masked protestors smashed windows and clashed with police.
Officers responded with tear gas, pepper spray, stun grenades and water cannons to disperse the demonstrators.
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