DONALD Trump has lashed out at members of his own party as his controversial response to white supremacist violence threatens to engulf his presidency.

With prominent Republicans openly questioning his competence and moral leadership, Mr Trump returned to the racially charged debate over Confederate memorials, bemoaning efforts to remove them as an attack on America’s “history and culture”.

And he berated his critics who, with increasingly sharper language, have denounced his initially slow and then ultimately combative comments on the racial violence at a white supremacist rally last weekend in Charlottesville, Virginia.

Mr Trump was much quicker on Thursday to condemn violence in Barcelona, where 13 people were killed in a terrorist attack when a van sped down Las Ramblas tourist spot.

He then added a tweet reviving a debunked legend about a US general subduing Muslim rebels a century ago in the Philippines by shooting them with bullets dipped in pig blood. The president wrote: “Study what General Pershing did to terrorists when caught. There was no more Radical Islamic Terror for 35 years!”

Mr Trump’s unpredictable, defiant and, critics claim, racially provocative behaviour has clearly begun to anger his Republican allies.

Senator Bob Corker of Tennessee, who Mr Trump considered for a Cabinet post, declared “the president has not yet been able to demonstrate the stability nor some of the competence that he needs to” in dealing with crises.

And Senator Dan Sullivan of Alaska tweeted: “Anything less than complete & unambiguous condemnation of white supremacists, neo-Nazis and KKK by the @POTUS is unacceptable. Period.”

Senator Tim Scott of South Carolina, a Republican African-American, said that the president’s “moral authority is compromised”.

Mr Trump, known to try to change news coverage with an attention-grabbing declaration, sought to shift focus from the white supremacists to the future of statues.

“You can’t change history, but you can learn from it,” he tweeted. “Robert E Lee. Stonewall Jackson - who’s next, Washington, Jefferson? So foolish.”