Four in five victims of child sexual abuse in Australian institutions are now eligible for compensation after three churches, the Scouts movement and the YMCA joined a federal government redress plan, an official said on Thursday.

The Catholic Church, Australia's largest denomination, on Wednesday became the first non-government institution to commit to the 3.8 billion Australian dollar (approx. 2.9 billion US dollars) national plan.

The Anglican Church, Salvation Army, Scouts Australia and the Young Men's Christian Association, better known as YMCA, committed to join on Thursday.

Flanked by representatives of the churches and associations, Social Services Minister Dan Tehan said their participation meant that 80 percent of Australia's 60,000 known abuse victims were now covered by the plan.

The Catholic Church estimates it alone will be liable for about 1 billion Australian dollars (approx. 757 million US dollars) in compensation.

Archbishop of Adelaide Philip Wilson last week became the most senior Catholic cleric in the world to be convicted of covering up child sex abuse.

He faces a potential two-year prison term when he appears in court in June to be sentenced for protecting a paedophile priest in the 1970s.

Pope Francis' former finance minister, Cardinal George Pell, faces trial on sexual assault charges in Australia.

The exact details and nature of the charges have not been disclosed to the public, though police have described them as "historical" sexual assaults, meaning they are alleged to have occurred decades ago.

Catholic leaders have long backed a national redress plan but the churches, charities and other non-government institutions needed the state and territory governments to sign on first.