Donald Trump headed for Capitol Hill on Tuesday afternoon facing a backlash from his own party – and the American public – over his policy of separating children from their parents at the southern US border.

The separations occur when, under a “zero tolerance” immigration policy, adults are arrested for crossing the border illegally. As children cannot be held in an adult jail, they are held separately.

According to a Quinnipiac University national poll, two in three voters oppose the separations. Outcry from Democratic and Republican politicians, former first ladies, churches, commentators and business leaders is gathering momentum.

President Trump, however, seems determined only to up the ante. On Tuesday morning he tweeted that Democrats want undocumented migrants “to pour into and infest our country”. In a lunchtime speech to the National Federation of Independent Business (NFIB), he said the US had two options: “Totally open borders or criminal prosecution for lawbreaking.”

Tim Malloy, assistant director of the Quinnipiac poll, asked: “When does public opinion become a demand that politicians just can’t ignore? Two-thirds of American voters oppose the family separation policy at our borders. Neither quotes from the Bible, nor get-tough talk can soften the images of  crying children , nor reverse the pain so many Americans feel.”

Trump’s campaign was built around a tough stance on immigration, with “build the wall” a frequent chant at his presidential election rallies. He is now losing the battle for public opinion, though support among his base is still strong.