When Michael Bloomberg was on the verge of running for mayor of New York City in 2001, he quietly resigned from several elite social clubs that primarily or exclusively counted white people ― and often only men ― among their members.

But once the spotlight of public office was off Bloomberg, he began rejoining some of these clubs. The New York Post’s PageSix section noted in 2014 that Bloomberg had rejoined the Century Club, a predominantly white club in Purchase, New York. He also put his children up for membership, the Post reported at the time.

Now, HuffPost has learned Bloomberg also rejoined The Brook club — an elite, secretive social club in midtown Manhattan. It’s difficult to even come by a picture of the inside of the club, and often the only way to discern members is when they list it in their obituary. It has been widely reported to be a men’s-only club, including when Bloomberg resigned in 2001.

As long as The Brook and similar clubs keep their membership under 400, they are able to avoid nondiscrimination laws and bar women. Several press reports have noted the club does allow women in for special events, however. A man who answered the phone at The Brook on Thursday told HuffPost that the club is not an all-male organization, but did not elaborate.

“My understanding is also that The Brook club has female members and people of color as members today, at some point in the past they were male only,” Stu Loeser, a campaign spokesman for Bloomberg, told HuffPost Wednesday.

JEFF KOWALSKY via Getty Images Democratic presidential candidate and former New York Mayor Michael Bloomberg speaks at a campaign stop at Eastern Market in Detroit, Michigan, on Feb. 4, 2020.

Bloomberg’s memberships to social clubs like The Brook is reflective of the elite world that he’s inhabited for most of his life. The businessman, whose estimated net worth is around $53 billion, has refused any campaign contributions ― spending over $300 million of his own money on his campaign since entering the presidential race in November. Critics and fellow candidates alike have questioned if the billionaire media mogul will be able to assemble a broad and diverse coalition of voters to deliver him the Democratic nomination.

Loeser also confirmed Bloomberg is still a member at the Century Country Club. The Century Country Club was founded by Jewish men in the mid-1800s, and has a similar air of exclusivity. The club does accept female members, but the majority of its members are white.

In 2001, Arthur Levitt, a former chair of the Securities and Exchange Commission and fellow member of the Century Country Club, where he was Bloomberg’s golf partner, told The New York Times that “I think there are probably a limited number of non-Jewish members.”

“I have seen Blacks and I have seen Hispanics, but I have no idea whether they are members or not,” he continued. “Somebody told me there was a Black member, but you could hardly say there was lavish representation of the Black or Hispanic community at Century, or any other club, for that matter.”

At the time he quit the Century Country Club, The Brook and the two others ― the Racquet and Tennis Club and the Harmonie Club ― Bloomberg said they were not diverse enough for him to keep his membership.

“I have urged the membership committees of the clubs to consider as many different applicants as they possibly can and to take an active stance in trying to make sure that they get as good a group of people as they can, but a diverse group of people,” Bloomberg said at a news conference in July 2001.

“Those clubs have a right to do what they want, but if I can’t change them, and I choose to resign, then I have chosen to go elsewhere,” he added.

Loeser told HuffPost on Wednesday that Bloomberg rejoined both the Century Country Club and The Brook after he left office in 2013. Loeser claimed that the Century Country Club has become more diverse since Bloomberg left his role as mayor.

“After serving as mayor, Mike found that clubs which had been formed as much as a century ago by Jewish families had changed in recent decades,” Loeser said of Bloomberg’s membership with the Century Country Club. “Just as families in the broader Jewish community had changed over time, the clubs had become far more interracial and more interfaith.”

The Century Country Club did not respond to HuffPost’s request for comment.

Bloomberg has come under fire for the controversial “stop and frisk” crime prevention strategy commonly practiced while he was mayor of New York City. The strategy has been widely criticized as racially discriminatory. Earlier this week, an audio clip from 2015 resurfaced of Bloomberg defending stop and frisk in which he says “all the crime” can be found in minority neighborhoods.