Donald Trump
Donald TrumpReuters

Presumptive Republican presidential nominee Donald Trump was under fire from Republicans on Tuesday after hinting that a judge presiding over a lawsuit involving his business was biased because of his Mexican heritage.

The judge in question is federal Judge Gonzalo Curiel, who is overseeing a lawsuit on Trump University.

Senate Republican leader Mitch McConnell blasted Trump and called on him to stop attacking minority groups and start talking about issues that Americans care about.

"My advice to our nominee is to start talking about the issues that the American people care about, and to start doing it now," McConnell told reporters when asked about Trump's attacks, according to the Reuters news agency.

"In addition to that, it's time to quit attacking various people that you competed with or various minority groups in the country and get on message," added McConnell.

Also ripping Trump’s remarks was House Speaker Paul Ryan, who said they were "the textbook definition of a racist comment", according to CNN.

Ryan added that the firestorm over Trump's comments was undercutting his own push to roll out a positive policy agenda for his party. He said he wouldn't defend Trump but instead would concentrate on his agenda project.

"I disavow those comments," Ryan stressed.

Pressed on whether he regretted his own endorsement of Trump that came last week, Ryan added, "I regret those comments he made."

"It's absolutely unacceptable," he said, according to CNN, though he stressed that he stood by his support for Trump. "Do I think Hillary Clinton is the answer? No I do not."

Ryan said that ultimately he has more in common on the policy issues of the day with Trump and better odds of getting those proposals enacted into law.

Meanwhile, Trump himself sought Tuesday to quell the criticism and explained his remarks had been "misconstrued."

In a lengthy statement quoted by CNN, Trump tried to explain his comments about Judge Curiel, explain that he does not believe "one's heritage makes them incapable of being impartial."

"Based on the rulings that I have received in the Trump University civil case, I feel justified in questioning whether I am receiving a fair trial," Trump clarified.

He added that he also has "concerns as to my ability to receive a fair trial" due to his status as the Republican Party's nominee and his campaign's focus on illegal immigration.

"Normally, legal issues in a civil case would be heard in a neutral environment. However, given my unique circumstances as nominee of the Republican Party and the core issues of my campaign that focus on illegal immigration, jobs and unfair trade, I have concerns as to my ability to receive a fair trial," Trump said, adding that he does "not intend to comment on this matter any further."

Trump had previously come under fire over his calls to temporarily ban Muslims from entering the United States due to security concerns.

He later softened his tone on this issue and explained that the comments were “just a suggestion”.