Two conservative cardinals have linked a "homosexual agenda" to crimes against children ahead of a major Vatican summit on the prevention of sexual abuse.

Key points: The letter says the "horrible crime" of child abuse is "only part of a much greater crisis"

The letter says the "horrible crime" of child abuse is "only part of a much greater crisis" The Brisbane Archbishop rejects the letter, saying the problem lies in abuse of power

The Brisbane Archbishop rejects the letter, saying the problem lies in abuse of power The Vatican is holding a summit on the prevention of child sexual abuse

In an open letter American Cardinal Raymond Burke and German Cardinal Walter Brandmuller argued the abuse of children in Catholic institutions was not solely caused by an abuse of power by clergy but was "part of a much greater crisis".

"The plague of the homosexual agenda has been spread within the church, promoted by organised networks and protected by a climate of complicity and a conspiracy of silence," they wrote.

Both cardinals are outspoken critics of Pope Francis and belong to a traditionalist wing of the Church that includes many that believe homosexuality is the main cause of clerical abuse.

Archbishop of Brisbane, Mark Coleridge — one of Australia's most senior Catholics — said he disagreed "totally" with the letter and its contents.

"[The] two cardinals are renowned for this kind of critique, which I and many others simply reject out of hand," he said from the Vatican.

"As far as I and Pope Francis and many others can see the problem is the abuse of power."

Brisbane Archbishop Mark Coleridge said he rejected a letter written by two controversial cardinals that linked clerical sexual abuse of children with a "homosexual agenda". ( ABC News: Lincoln Rothall )

Archbishop Coleridge said there must be some concrete steps for bishops to follow after the summit, otherwise it would be seen as lip service.

"I think the time for words is long, long past," he said.

"I think [we need] an action that is grounded upon a recognition that we're dealing with a global emergency, and I don't think the word is too strong."

Sorry, this video has expired Abuse survivors react to meeting with senior Catholic figures

Victims of church abuse were also quick to condemn the letter.

On Wednesday 12 victims met with prominent cardinals who organised the summit and said people's faith in the Vatican was "washing away".

American Phil Saviano was one of the survivors at the meeting.

His story was told in the movie Spotlight after he gave information to journalists, which led to a major investigation into child abuse perpetrated by the Boston clergy.

Mr Saviano said blaming gay priests for the widespread abuse of children was inaccurate and a deflection.

"I think that trying to lump it all together on homosexuality is A: it's a dodge, B: it's not psychologically accurate," he said.

"It's not going to lead to a proper solution and it's also an insult to all of the women who have been sexually abused as children."

The Vatican said Pope Francis called the landmark summit of 190 bishops and heads of Catholic religious orders to ensure church leaders are accountable to victims.

Pope Francis is hosting a summit on the prevention of child sex abuse. ( AP: Andrew Medichini )

Last week, the pontiff expelled Theodore McCarrick, a former cardinal and archbishop of Washington, after the Vatican found him guilty of sexually abusing children and seminarians.

The move appears to be the first time any cardinal has been defrocked for sexual abuse.

Pope Francis has previously said he was "concerned" about the issue of homosexuality within the clergy.

"The issue of homosexuality is a very serious issue that must be adequately discerned from the beginning with the candidates," he said in the book The Strength of Vocation, which was released in December 2018.