By Mariano Castillo and Richard Allen Greene, CNN
(CNN) -- In an unprecedented report, a United Nations committee slammed the Vatican's handling of child sexual abuse within the Catholic Church and accused the church of protecting itself rather than the victims.
The Vatican should establish an "independent mechanism for monitoring children's rights" to investigate complaints and work with law enforcement, according to the report, which was released Wednesday.
It calls for the church to immediately remove all known or suspected abusers from its ranks.
The permanent observer of the Holy See to the United Nations, Archbishop Silvano Tomasi, said the Catholic Church has done much for the protection of children, but should do more.
"We have to continue to refine, to enact provisions that protect children in all their necessities so that they may grow and become productive adults in society and their dignity be constantly respected," he told Vatican Radio.
The report follows a hearing last month where Vatican officials were grilled over the church's handling of child abuse allegations.
The Vatican, as a country, is a signatory of the U.N. Convention of the Rights of the Child, and it was the U.N. Committee on the Rights of the Child that published the report.
Clerics have been involved in the sexual abuse of "tens of thousands" of children, the report says, and the United Nations is concerned about how the Vatican has handled the allegations.
"The committee is gravely concerned that the Holy See has not acknowledged the extent of the crimes committed, has not taken the necessary measures to address cases of child sexual abuse and protect children, and has adopted policies and practices which has led to the continuation of the abuse by and the impunity of the perpetrators," the report states.
The Vatican on Wednesday said it will study the report. Tomasi said the church does more than "other institutions or even other states" to prevent further child abuse.
He criticized the U.N. report for saying the church should accept the practice of abortion.
"This is a contradiction with the principle of life that the convention itself should support, recommending that children be protected before and after birth," he said.
The report accuses the Vatican of transferring child sexual abusers from one parish to another in an attempt to cover up crimes, placing children at high risk for abuse.
"The Holy See has consistently placed the preservation of the reputation of the Church and the protection of the perpetrators above children's best interests," the report states.
Closed-door proceedings have allowed a majority of abusers to avoid criminal proceedings, the report says. A "code of silence" within the clergy ensures that many cases of child sexual abuse are not reported to law enforcement, according to the report.
Last month, the Vatican acknowledged that close to 400 priests left the priesthood in 2011 and 2012 because of accusations that they had sexually abused children.
Since taking the helm of the Roman Catholic Church in March, Pope Francis has told a senior Vatican official to carry out "due proceedings against the guilty" in sexual abuse cases.
The report also called on the Vatican to make it mandatory to report all cases of suspected child abuse to law enforcement.
The report rejected a Vatican argument that it, the Holy See, is only responsible for people who live in the tiny Vatican city-state. The U.N. says the Vatican has supreme power over individuals and institutions under its authority.
One advocacy group, the Survivors Network of those Abused by Priests , said the report is evidence that Vatican claims of reform are deceptive.
It is "utterly tragic" that a body like the U.N. must tell the church to kick out abusers, the group said.
"That is, of course, common sense and common decency," SNAP said in a statement. "That the church hierarchy must be told this is damning."
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