Two giants of Roman Catholicism in the 20th century will become saints today at a twin ceremony that has aroused both joy and controversy in the 1.2 billion-member Church.

Pope John XXIII, who reigned from 1958 to 1963 and called the modernising Second Vatican Council, and Pope John Paul II, who reigned for nearly 27 years before his death in 2005, will be canonised by Pope Francis.

But critics say the canonisation of John Paul is wrong as he was slow to grasp the seriousness of the child sexual abuse crisis.