Washington DC - Sonia Sotomayor has become the latest Supreme Court justice to spark ethics concerns after it came out her staff pressured libraries and universities to buy her books.

Sotomayor's taxpayer-funded staff have over the years been involved in organizing events designed to sell the justice's memoir and children's books and encouraging public institutions to purchase more of the books ahead of her appearances, an Associated Press investigation has found.

The Bronx native has earned at least $3.7 million from book sales since her confirmation to the court in 2009.

In one notable email exchange ahead of a 2019 book talk at Oregon's Multnomah County Library, Sotomayor's aide Ahn Le wrote, "250 books is definitely not enough. Families purchase multiples and people will be upset if they are unable to get in line because the book required is sold out."

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In other sectors of government, staffers would be barred from promoting an official's literary ventures in this way, but the Supreme Court's lack of an ethics code leaves the possibility open for justices.

The liberal justice has also failed to recuse herself from several prior SCOTUS cases involving her publisher, Penguin Random House, though the court said she would have done so had those cases gone for review.

The revelations over Sotomayor come amid national outcry over conservative Justices Clarence Thomas and Samuel Alito's undisclosed gifts from wealthy GOP donors.

The discoveries have been particularly controversial given the Supreme Court's recent string of rightwing decisions on abortion rights, affirmative action, partial student loan cancelation, and more.

Reform advocates are increasingly demanding a tighter ethics code and expansion of the Supreme Court with the addition of four new justices.