Mitt Romney has urged the Republican Party to reject Donald Trump, reportedly calling the front-runner a “phony” and “fraud”.
The former Republican presidential candidate accuses Donald Trump of “playing the American public for suckers”, in a planned speech leaked to the media.
Donald Trump has meanwhile mocked Mitt Romney on Twitter as a “failed candidate” who should not advise on getting elected.
Many senior Republicans are alarmed at the prospect of Donald Trump securing the nomination for November’s election.
In the latest attack from top figures in the party, several members of the Republican national security community wrote an open letter describing Donald Trump’s “vision of American influence and power in the world” as “wildly inconsistent and unmoored in principle”.
“He swings from isolationism to military adventurism within the space of one sentence,” the letter said.
Donald Trump has sought to present himself as a “unifier”, after his victories in seven states on so-called Super Tuesday consolidated his position at the front of the race for his party’s nomination.
Mitt Romney, who has been a fierce critic of Donald Trump, is expected to warn in his speech on March 3 that his policies are a threat to the Republican Party and to the country as a whole.
“Here’s what I know: Donald Trump is a phony, a fraud,” Mitt Romney says, according to a leaked transcript of his remarks.
“His promises are as worthless as a degree from Trump University,” he is quoted as saying.
Mitt Romney will also warn that the nomination of Donald Trump would pave the way to the presidency for Democratic rival Hillary Clinton.
Donald Trump meanwhile accused Mitt Romney of having run “one of the worst races in presidential history” and “working with the establishment” to prevent a Republican win.
Mitt Romney lost the 2012 election to President Barack Obama.
Several GOP leaders, including House Speaker Paul Ryan and South Carolina Senator Lindsey Graham, have spoken out against Donald Trump’s controversial policies and positions in recent days.
Donald Trump’s latest controversy centers on his failure to disavow David Duke, a leader of the white supremacist Ku Klux Klan, who endorsed him. He later said he had on several occasions in the past disavowed David Duke.
Paul Ryan said on March 1 that nominees “must reject any group or cause that is built on bigotry. This party does not prey on people’s prejudices”.
Donald Trump rival Marco Rubio indicated in his speech on Super Tuesday that the Republican establishment was unlikely to back the former reality TV star.
According to the New York Times, some GOP donors are already trying to raise funds for an anti-Trump effort.