The United Nations is failing some of the most vulnerable children it is supposed to protect. A decade ago, the organization acknowledged that some of the peacekeepers sent to international conflict zones were sexually abusing local women and children, and it promised corrective action. The scourge continues, prompting one senior U.N. official to recoil at what he called the “constant horror story of allegations” against the peacekeepers.

The latest accusations, like ones that have gone before, discredit the U.N. and everything it stands for, not least a commitment to help restore stability, public safety and the rule of law to countries ravaged by civil war or international conflict. They also indict many of the governments that contribute troops for peacekeeping operations by highlighting their refusal or inability to end the culture of denial that allows these abuses to go on.

This month, Human Rights Watch said that at least eight women and girls were raped or sexually exploited last year in the Central African Republic by troops from the Republic of Congo and the Democratic Republic of Congo. Last week, U.N. officials said four minors, residents of a camp for displaced persons in the Central African Republic, had reported abuse and exploitation in 2014 and 2015 by peacekeepers from the Democratic Republic of Congo.

The new cases are in addition to U.N. disclosures last month that it had received evidence of abuse of a dozen other children in the Central African Republic in 2014 and 2015. In six of these cases, the accused included troops from France, Georgia and an unidentified European country. The other six victims accused peacekeepers from Bangladesh, the Democratic Republic of Congo, Niger, and Morocco, and U.N. police officers from Senegal.

Foreign troops were deployed in the Central African Republic after mainly Muslim rebels seized power in the majority-Christian country in 2013. But allegations of sexual abuse by peacekeepers date at least to the 1990s in the Balkans, Cambodia, and East Timor, and to 2002 in West Africa. In 2003, the U.N. declared a zero-tolerance policy, banning all forms of prostitution and sexual activities with people younger than 18.

The problem persisted. A year later, the organization produced a blistering report on abuse in the Democratic Republic of Congo, followed by efforts to improve training and enforcement. The reforms did not happen or they fell short. Recently, a U.N. official said abuses in the Central African Republic were “rampant.”

Countries that contribute troops to vital multimillion-dollar peacekeeping missions bear the primary responsibility for crimes committed by their forces. But the U.N. urgently needs to intensify its oversight, documenting abuse cases; keeping better track of whether the abuses are followed up with prosecutions, and holding countries publicly accountable when they let abusive troops off the hook, which seems to be the pattern.