Bogdan Klich, Poland's chargé d'affaires, said in a letter that he was "outraged" by what he called "false and deeply disturbing statements" Carlson made during a podcast interview with Sir Jacob Rees-Mogg, a former British minister and prominent Brexit supporter.
Carlson had argued that Germany was stripped of "German territory with Germans in it" before the war.
Rees-Mogg countered that Prussia had earlier taken part in the partitions of Poland.
Carlson did not address that point, saying instead that this had been Hitler's argument "and by the way, that was true."
He went on to claim Britain should not have entered a war that brought it no benefit and cost it its empire and sovereignty.
Klich described the remarks as a "colossal insult to the millions of victims of Nazism, including hundreds of thousands of American soldiers who had been killed or wounded while liberating Europe."
He said Britain and France did not declare war on Germany merely out of duty to an ally, arguing they would have been attacked regardless.
The invasion of Poland, he added, was "meticulously planned," with the aim of destroying the Polish state, exterminating its people and continuing a bloody conquest of the world.
"As an American journalist who enjoys the democratic right to the freedom speech, you have now become an apologist for Adolf Hitler," Klich wrote, accusing Carlson of lying and falsifying documented historical facts.
He demanded an immediate and public retraction and apology.
"Nazi propaganda cannot be rehabilitated under the guise of free speech," he said.
During the interview, Rees-Mogg repeatedly challenged Carlson's claims, saying he was "verging on defending Hitler."
Carlson replied that he was not a "secret Nazi."
Carlson, a former Fox News host known for pro-Russian views, has previously expressed sympathy for Vladimir Putin's Russia and suggested it is superior to the West.
In the same interview, he claimed, contrary to the facts, that Russia's economy is "much larger" than Britain's.
He has also criticised the Allied war effort against Nazi Germany before, and has hosted the historian Darryl Cooper, known for revisionist views and for downplaying Hitler's role.
(ał/gs)
Source: PAP