Donald J. Trump on Monday said his campaign would revoke the press credentials of The Washington Post, effectively prohibiting journalists from one of the nation’s largest newspapers from joining the traveling press corps of the presumptive Republican nominee.

Barring journalists is an almost unheard-of practice for a modern presidential candidate. The Post is the latest major news organization that Mr. Trump has barred from his rallies and events this year, following Politico, BuzzFeed News, The Huffington Post and others.

In a Facebook post on Monday, Mr. Trump accused The Post of “incredibly inaccurate coverage and reporting” and deemed it “phony and dishonest,” although he has granted frequent interviews to the paper’s editors and reporters in the past.

It was not immediately clear if Mr. Trump’s announcement meant he would end all his communications with Post journalists. Mr. Trump has a propensity to attack the news media, but he is also a keen cultivator of journalists, and he has been known to criticize reporters, then meet with them cordially shortly afterward.