New York City’s housing authority promised in June as part of a landmark legal settlement to correct years of maintenance failures, mismanagement and cover-ups that federal authorities said had exposed 400,000 public housing residents to lead paint and other health hazards.

But on Friday, the United States attorney’s office severely criticized the authority for failing to live up to a key part of that agreement, or consent decree: a promise to immediately take precautions in thousands of apartments to protect residents — including children — from toxic dust and other hazardous particles that are dispersed when workers strip or seal lead paint.

The government took the New York City Housing Authority, or Nycha, to task in a court filing for failing to follow safe work practices and for not letting the United States attorney’s office know the authority had been violating its promise until officials asked. Then, the government said, the authority had argued incorrectly the agreement did not impose a deadline for adopting the safety guidelines.

“This effort to excuse Nycha’s clear-cut violation of the consent decree is consistent with the culture of apathy and deception, and demonstrates the need for independent oversight,” the office of Geoffrey S. Berman, the United States attorney for the Southern District of New York, said in the filing.