Instead of attacking CEO Jeff Bezos, President Donald Trump should start fact-checking his tweets, angel investor and Inside.com CEO Jason Calacanis told CNBC on Wednesday.

Trump incorrectly tweeted Wednesday morning that Amazon owns the Washington Post to avoid paying a so-called "internet tax," when in fact it is Jeff Bezos — not Amazon — that owns the media company.

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"Amazon pays their taxes," said Calacanis. "This is a completely fake tweet. It's fake news."

"Nobody believes what Trump is saying anymore. He tweets at 5:00 a.m.; nobody vets the tweets. It's a complete embarrassment for our country that the president is tweeting factually incorrect stuff," he said.

This isn't the first time Trump has targeted Bezos. At a campaign rally in February 2016, then candidate Trump told the crowd: "If I become president, oh [does Amazon] have problems. They're going to have such problems." He added that Bezos only bought the Post to have "political influence."

"Donald Trump can't hold a candle to what Jeff Bezos has added to society. He's created millions of jobs and is a tremendous innovator. Bezos is going to give his money away — he's done an amazing thing for America," Calacanis said on Squawk Alley.

Amazon did not immediately respond to CNBC's request for comment.