Former US ambassador to Australia Jeff Bleich has attacked US President Donald Trump's executive order on immigration, describing it as "illegal and cruel".

Mr Bleich said he had no choice but to condemn the executive order "as an American, a patriot, and a human being".

"President Trump's Executive Order banning all refugees from entering the United States and seeking asylum is illegal and cruel, and it violates the most basic tenets of our nation," he said in a statement.

"This land was settled by people seeking freedom from religious persecution. Barring access to all asylum seekers not only breaks the law, it breaks faith with who we are as a people."

Mr Trump's executive order placed a 90-day ban on immigration from seven Muslim-majority nations: Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen.

Mr Bleich, who served as US ambassador in Australia from 2009 to 2013, said he had never before issued a statement condemning the US Government but felt compelled to do so.

"From the time of its founding, this nation has given asylum to people from around the world forced from their homes by persecution or violence in their country," he said.

"I take no pleasure in condemning our nation's actions, but the hottest places in hell are reserved for those who in times of great moral crisis, maintain their neutrality."

He said people should celebrate the "profound contributions" that refugees have made to America.

The Federal Opposition has also weighed in on the issue, calling Prime Minister Malcolm Turnbull "spineless and weak" for refusing to condemn Mr Trump's temporary immigration ban.

But Immigration Minister Peter Dutton defended the Prime Minister's claim that it was "not his job" to comment on US policy, saying his comments were responsible and measured.