WASHINGTON — The White House moved Tuesday toward restoring historical press access norms by scrapping the mysterious pre-screening of reporters for one of President Biden’s large indoor events in the East Room — weeks after 73 reporters signed a letter demanding an end to the procedure.

For the first time in Biden’s presidency, roughly 50 journalists, including print reporters, TV correspondents and photographers, were let into the East Room without discrimination based on the outlet they represent — a departure from the non-transparent screening practice that has outraged the White House press corps for more than a year.

The East Room is the White House’s largest indoor space — nearly 3,000 square feet — and Tuesday’s event was “open press,” meaning that any journalist on the White House grounds was allowed to attend.

The easing of press access to the East Room occurred more than 14 months after the much smaller White House briefing room ended COVID-19 attendance caps and returned to full capacity in June 2021.

The prescreening of reporters for Biden’s events is widely understood to be a way to shape the questions he gets asked and no objective criteria for selection has ever been divulged.

Biden did not answer shouted questions at the Tuesday event, including about the FBI’s Monday raid on former President Donald Trump’s residence in Palm Beach, Fla. Instead, Biden signed documents approving the admission to NATO of Finland and Sweden and departed after briefly mingling with guests.

Reporters excluded from most other Biden events murmured their approval of the restoration of access norms for the East Room, but the change apparently won’t be a complete aboutface. On Tuesday night, the White House indicated that a Wednesday bill-signing event in the East Room would again be limited to reporters chosen via the prior non-transparent process.

The White House did not respond to The Post’s request for comment and the Tuesday status change went unmentioned by Biden’s spokespeople aside from being noted on the daily press schedule.

It’s unclear if other venues traditionally open to all journalists, such as the large auditorium in the White House-adjacent Eisenhower Executive Office Building, will resume open press access as well.

In late June, 73 reporters signed a letter demanding an end to the pre-screening of reporters let into Biden’s events after it resulted in journalists from some large news outlets, including The Post, going up to seven months without being admitted to an indoor event.

Senior journalists, including leaders of the White House Correspondents’ Association, struggled for more than a year to understand or abolish the pre-screening — warning that curating the group of reporters allowed within earshot of Biden would set a troubling precedent.

“Who is blocked today may be different from who is blocked tomorrow — and since access curbs tend to stick around, it’s a worthwhile fight,” Washington Post media critic Erik Wemple wrote in a July column.

The Correspondents Association’s outgoing president, Steven Portnoy of CBS News Radio, helped lead the June protest letter, which was written by veteran reporter Brian Karem of Salon and circulated by a reporter from The Post.

Former association president Tom DeFrank of National Journal told The Post he signed the letter because it was important to stop the erosion of historical norms.

“Having covered the White House since June of 1968 as a Newsweek intern, I’ve seen a troubling erosion in access that was once routine,” DeFrank said at the time.

A number of high-profile journalists also supported the protest letter, including CNN’s Kaitlan Collins, CBS’s Ed O’Keefe, Fox News’ Jacqui Heinrich, Axios’ Jonathan Swan, The New York Times’ Peter Baker and Maggie Haberman, former ABC anchor and White House reporter Sam Donaldson, TheGrio’s April Ryan, Newsmax’s James Rosen, Gray Television’s Jon Decker and Al Jazeera’s Kimberly Halkett.

White House press secretary Karine Jean-Pierre said at a June briefing that “I actually don’t know” how the selection process worked, but denied it amounted to “blacklisting” of certain outlets or reporters. Former White House press secretary Jen Psaki in October declined to share the criteria, saying at a briefing, “I don’t have any more information on that.”

Reporters were given a wide range of conflicting explanations of how the selection process worked, causing frustrations to mount. One journalist who signed the letter said he was told by a prominent press officer that a random number generator determined who got in — though that wouldn’t explain why some news outlets went so long without selection.

Prior explanations offered by White House staff to reporters indicated the process was “first come, first served,” which was anecdotally debunked, or that there was some sort of rotation in effect for outlets based on their size.

The protest letter called out the lack of clarify and urged the White House to change course.

“The current method of allowing a limited number of reporters into these events is not only restrictive and antithetical to the concept of a free press, but it has been done without any transparent process into how reporters are selected to cover these events,” the protest letter said.

“The continued inability of the White House to be candid and transparent about the selection process for reporters attf his remarks undermines President Biden’s credibility when he says he is a defender of the First Amendment,” it continued.

“The incongruity of these restrictions underscores the belief by many reporters that the administration seeks to limit access to the president by anyone outside of the pool, or anyone who might ask a question the administration doesn’t want asked.”

“Let us be candid,” the letter went on. “Our job is not to be liked, nor is it to be concerned about whether or not you like what we ask. Reporters’ ability to question the most powerful man in our government shouldn’t be discretionary. The administration’s continued efforts to limit access to the president cannot be defended.”

The letter added, “Any notion that space is ‘limited’ is not supported by the fact that every other president before Biden (including Trump) allowed full access to the very same spaces without making us fill out a request form prior to admittance… We ask you to see to it that the protocols are changed back to the access norms to which we are accustomed.”