Theresa May has said it is important to condemn far-right views “wherever we hear them” as she was asked about Donald Trump’s response to clashes in the United States.
The PM said: “I see no equivalence between those who propound fascist views and those who oppose them.”
President Trump has faced criticism for blaming both sides for the violence in Charlottesville, Virginia.
A woman was killed when a car hit people opposed to a far-right rally.
The UK prime minister added: “I think it is important for all those in positions of responsibility to condemn far-right views wherever we hear them.”
She was speaking on a visit to Britain’s new aircraft carrier HMS Queen Elizabeth, in Portsmouth, her first engagement since her summer holiday.
Asked about Mr Trump’s response to the Charlottesville incidents, she said: “As I made clear at the weekend following the horrendous scenes that we saw in Charlottesville, I absolutely abhor the racism, the hatred and the violence that we have seen portrayed by these groups.
“The United Kingdom has taken action to ban far-right groups here, we have proscribed certain far-right groups here in the United Kingdom.
“And there is no equivalence.”
After widespread criticism of his initial response, Mr Trump had condemned white supremacist groups on Monday.
But at a press conference on Tuesday, he said there was “blame on both sides”.
“You had a group on one side that was bad,” he said.
“You had a group on the other side that was also very violent. Nobody wants to say that. I’ll say it right now.”
Leading figures in Mr Trump’s Republican party have reacted angrily to his latest comments, with House Speaker Paul Ryan saying: “White supremacy is repulsive.. There can be no moral ambiguity.”
Two of Mrs May’s ministers, Sajid Javid and Sam Gyimah, attacked Mr Trump’s response in Tweets on Wednesday.
“The ‘leader of the free world’ loses moral authority when he cannot call fascism by its name,” Mr Gyimah wrote.
Mr Javid said he had learned as a child that neo-Nazis were “bad” and anti-Nazis “good” and it was “pretty obvious”.
And Scottish Conservatives leader Ruth Davidson tweeted: “The president of the United States has just turned his face to the world to defend Nazis, fascists and racists. For shame.”
A number of Labour MPs have called on Mrs May’s offer of a visit with state honours for Mr Trump to be withdrawn.
Shadow defence secretary Nia Griffith tweeted: “A state visit by #DonaldTrump would shame this country and betray all we stand for. Theresa May should revoke the invitation immediately.”
Nottingham South MP Lilian Greenwood said Mr Trump’s comments were “sickening” and a “new low”.
Lib Dem leader Sir Vince Cable said it would be “completely wrong” for Mr Trump’s state visit to the UK to go ahead.
“Donald Trump has shown he is unable to detach himself from the extreme right and racial supremacists,” he added.
On Monday, Labour leader Jeremy Corbyn criticised Mr Trump’s response, saying: “What happened in Charlottesville was the KKK [Ku Klux Klan] and its supporters, white supremacists, arrived in Charlottesville in order to cause trouble.
“Surely every president of every country in the world… should be able to condemn that.”