The White House has been forced to refute that Donald Trump is a white supremacist after the alleged Christchurch mosque shooter wrote that he admired the US President.

Acting White House chief of staff Mick Mulvaney told Fox News on Monday morning (Australian time) that the act of a disturbed individual cannot be blamed on any one politician.

Fox News’ interviewer Chris Wallace questioned Mr Mulvaney on past comments by the President, including those made in a 2016 CNN interview in which he said “I think Islam hates us”.

“The President is not a white supremacist. I’m not sure how many times we have to say that,” Mr Mulvaney said.

Mr Trump condemned the “horrible massacre” at the Christchurch mosques that left 50 people dead and many more injured, while the White House called the shooting a “vicious act of hate”.

Asked by a reporter on Friday if he considered white nationalism a rising threat around the world, Mr Trump said: “I don’t really. I think it’s a small group of people.”

The accused gunman’s document posted before the attack praised the US president as “a symbol of renewed white identity and common purpose” even though he did not support all his policies.

The reference revived criticism that Mr Trump has not been strong enough in condemning hate speech and has fomented anti-Muslim sentiment.

“I don’t think it’s fair to cast this person as a supporter of Donald Trump,” Mr Mulvaney said.

“Any more than it is to look at his eco-terrorist passages in that manifesto and align him with (Democratic House Speaker) Nancy Pelosi or Ms Ocasio-Cortez,” a Democratic congresswoman,” he said.

“This was a disturbed individual, an evil person,” Mr Mulvaney added.

Mr Trump attracted criticism in the days after a deadly white supremacist rally in Charlottesville, Virginia, in 2017 when he equated white supremacists with counter-protesters and said “both sides” were to blame.

“At the very least, he [Trump] is dividing people. They are using him as an excuse. And he… should be giving strong statements, public speeches defending Muslims in this world,” says Democratic presidential candidate Sen. Amy Klobuchar on the rise of hate #CNNSOTU pic.twitter.com/QfE5TeUztv

— CNN Politics (@CNNPolitics) March 17, 2019

Democratic Senator Amy Klobuchar called for Mr Trump to condemn bigotry against Muslims, saying his rhetoric exacerbated tensions.

“I don’t think you can actually take each of the murderous acts and say what role Donald Trump played, but I can tell you this – his rhetoric doesn’t help,” Ms Klobuchar told CNN.

“And many of these [far-right extremists], whether it was the person who tried to bomb Barack Obama or this murderer in New Zealand, have cited Donald Trump along the way,” she said.

“He, at the very least, should be giving strong statements, public speeches, defending Muslims in this world,” Ms Klobuchar said.

Senator Kirsten Gillibrand, a 2020 Democratic presidential candidate, on Friday tweeted that Mr Trump’s rhetoric “emboldened” white supremacists.

“Time and time again, this President has embraced and emboldened white supremacists–and instead of condemning racist terrorists, he covers for them, his isn’t normal or acceptable,” Ms Gillibrand posted after Friday’s mosque attacks.

-with AAP