“Amazon is getting away with murder, tax-wise. [Bezos is] using the Washington Post for power so that the politicians in Washington don’t tax Amazon like they should be taxed,” Trump told Fox News host Sean Hannity.

The accusation came in response to reports that the Post has assembled a team of 20 reporters to dig into Trump’s real-estate past. It also came as Trump faces pressure to publish his own tax returns.

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Trump said his team was getting calls from Post reporters every hour “asking ridiculous questions.” He said the reporters were “slopping” together information from bad sources in order to write a book full of “all false stuff.”

“[Bezos has] got a huge antitrust problem because he’s controlling so much. Amazon is controlling so much of what they’re doing,” Trump said, describing Amazon as a “monopoly” and complaining that “the whole system’s rigged.”

Bezos bought the Washington Post in 2013 in a deal valued at $250 million. Trump described this as “practically nothing,” saying Bezos owns the publication “as a toy.”

Amazon decided to unwind its tax-avoidance strategy in the EU last year, following pressure from regulators across the bloc. However, the European Commission’s antitrust department is still investigating Amazon’s tax deals with the duchy of Luxembourg, to see whether they constituted illegal state aid. The U.S. Inland Revenue Service is also investigating those deals.

Women’s rights group UltraViolet recently urged Amazon to stop selling Trump-branded menswear products, due to the presumptive Republican nominee’s racist and sexist behavior.