Waterloo, Iowa - Donald Trump has doubled down on his recent anti-immigrant remarks, and responded to critics who have been comparing him to Adolf Hitler.

The former president and current front-runner in the Republican primaries made the comments on Tuesday, where he repeated that immigration is "poisoning the blood of our country." The statement has received criticism from both sides of the political aisle.

"That's what they're doing - they're destroying our country," Trump said in a clip of the event. "They don't like it when I said that. And I never read Mein Kampf.

"They said, 'Oh, Hitler said that' - in a much different way," he added.

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Trump recently came under fire for using the phrase "poisoning the blood" at a rally in New Hampshire, and again at a rally in Nevada the following night.

Many critics quickly pointed out how Trump's rhetoric is very similar to that of Hitler's, who used the term "blood poisoning" in his book Mein Kampf, which was published in 1925.

"The adulteration of the blood and racial deterioration conditioned thereby are the only causes that account for the decline of ancient civilizations," Hitler wrote in a chapter titled Nation and Race.

During the rally, Trump also vowed that if he wins re-election, he will create a "federal task force on fighting anti-Christian bias" because "they are going after Christians in America."