Speaking to an audience in Washington DC, Ms Davidson described the White House as “chaotic” because of a lack of a “lack of professionalism and moral seriousness”.
And she said staff at the Trump administration were one step away from “white supremacist bloggers”.
She named Steve Bannon, President Trump’s chief strategist and former chairman of the far-right Breitbart News.
Ms Davidson also told audience members at the Women in the World event on Wednesday that the British government’s re-evaluation was part of a “massive, massive shock” induced across Europe by President Trump.
Referring to the UK-US relationship, she said: “We are going to want to make sure that any deals that are done he is going to honour. We have to be sure of that.”
Ms Davidson does not attend cabinet meetings but has an invitation to attend Prime Minister Theresa May’s “political cabinets”, when political strategy rather than government business is discussed.
Her comments come after the Prime Minister attempted to strike a friendly tone when she visited Mr Trump last month.
The Prime Minister also spoke to Mr Trump by phone on Valentine’s Day, and has said she “looks forward” to his state visit this summer.
The Scottish Tory leader also said caution was required with a President whose early actions should “worry us all”.
She added: “At the moment, from the UK, we have always seen America as being a very strong, a reliable ally and now, even after only 26 days or however long the tenure has been so far in Pennsylvania Avenue, we are beginning to reassess how reliable an ally the United States is.”