Hours before Mark Zuckerberg, the chief executive of Meta, was set to testify on Wednesday about child safety online, lawmakers released internal documents showing how his company had rejected calls to bulk up on resources to combat the problem.

In 90 pages of internal emails from fall 2021, top officials at Meta, which owns Instagram and Facebook, debated the addition of dozens of engineers and other employees to focus on children’s well-being and safety. One proposal to Mr. Zuckerberg for 45 new staff members was declined.

The documents, which are being released in full for the first time, were cited in a lawsuit last year by 33 state attorneys general who accused Meta of getting young users hooked on its apps. They contradict statements from company executives, including the head of global safety and the head of Instagram, who testified in congressional hearings on child safety during that period that they prioritized the well-being of their youngest users and would work harder to combat harmful content on their platform.

Mr. Zuckerberg, who will be testifying before Congress on Wednesday for the eighth time, is in the hot seat to defend Meta’s lack of investment in child safety amid rising complaints of toxic and harmful content online, said Senator Richard Blumenthal, Democrat of Connecticut, who released the emails with Senator Marsha Blackburn, Republican of Tennessee.

“The hypocrisy is mind-boggling,” Mr. Blumenthal said in an interview. “We’ve heard time and time again how much they care and are working on this but the documents show a very different picture.”

Meta has created more than 30 tools to help protect teens, and it has a “robust” team overseeing youth well-being, Andy Stone, a Meta spokesman, said in a statement, adding that “these cherry-picked documents do not provide the full context of how the company operates or what decisions were made.”