FRANKFURT—Germany’s central bank Monday said President Donald Trump’s tax plans would likely hurt the U.S. economy and lead to a 30 percentage-point increase U.S. debt-to-gross domestic product ratio within a decade.

The comments, published in the Bundesbank’s monthly report, represent a rare critique by the central bank of US economic policy, but come amid tensions between Berlin and the new administration in Washington, which has attacked Germany’s persistent trade surpluses.

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