Neil Gorsuch, Donald Trump’s nominee for the Supreme Court, has expressed dismay over the president’s attack on a “so-called” judge who blocked his controversial immigration order, highlighting mounting concerns about Mr Trump’s challenges to the integrity of the judiciary.

Mr Gorsuch told a Democratic senator that Mr Trump’s tweeted dismissal of the federal judge and his “ridiculous” opinion about the president’s travel ban on citizens from seven Muslim-majority nations was “demoralising” and “disheartening”.

Richard Blumenthal, the Connecticut senator, disclosed the comments after meeting Mr Gorsuch on Wednesday, ahead of confirmation hearings at which Democrats are under pressure from their base to try to block his nomination to fill the empty seat on the nine-justice court.

Mr Trump on Wednesday defended his travel ban against the lower court’s “horrible, dangerous and wrong” decision, saying that the appeals court now evaluating the immigration order should realise that he was acting within his legal authority, which he said a “bad high school student would understand”.

Speaking to law enforcement officials in Washington on Wednesday, Mr Trump read a statute that he claimed gave him the power to bar “any class” of foreigner from entering the US.

“You can suspend, you can put restrictions, you can do whatever you want,” he told an audience of police chiefs and sheriffs. “It just can’t be written any plainer or better.”

His comments came the day after an appeals court questioned his authority to impose the ban, which some critics claim infringes the constitutional ban on religious discrimination on the grounds that it was focused on countries where the majority of the population are Muslim. The White House had asked the court to reimpose the ban, which was temporarily suspended by a lower-court ruling last week.

Despite the criticism that erupted after his questioning of the lower court justice last week, the president on Wednesday alluded to concern about the liberal leanings of at least one of the judges on the three-member panel that heard the White House appeal.

“I don’t ever want to call a court biased, so I won’t call it biased,” Mr Trump said. “The courts seem to be so political, and it would be so great for our justice system if they would be able to read a statement and do what’s right, and that has got to do with the security of our country, which is so important.”

The continuing court battle over the travel ban came as Mr Trump’s nominee for attorney general to head the federal Department of Justice passed a vote on final confirmation on Wednesday.

Jeff Sessions, a Republican senator from Alabama, was confirmed in a narrow 52-47 vote in the US Senate.

Mr Sessions will replace Dana Boente, the acting attorney general. Mr Boente was chosen by Mr Trump to replace Obama administration appointee Sally Yates, whom the president fired when she refused to defend his controversial travel ban.

While presidents often comment on court rulings they dislike, critics say Mr Trump’s disparaging remarks about the district court judge who suspended the immigration order marks a dangerous development.

During the presidential campaign, Republicans joined Democrats in chastising Mr Trump after he said Gonzalo Curiel, an Indiana-born judge who ruled against him in a case about Trump University, should recuse himself due to his “Mexican heritage”.