'How much worse does it get?': Pedophile priest John Sidney Denham has 13 years added to jail term

Pedophile priest John Sidney Denham will spend at least 19 years and five months in jail after being sentenced for systematically abusing dozens of vulnerable boys.

Denham, 73, had already been jailed for at least 14 years in 2010 for his "sadistic" sexual assault of boys as young as five.

But today Judge Helen Syme sentenced him to at least another 13 years for the abuse of another 18 boys, describing his crimes as some of the worst the courts have ever seen.

"As the crown rhetorically asks, `How much worse does it get?'" she stated.

Judge Syme said he treated St Pius X as "his own pedophilic smorgasbord", with dozens having complained of abuse over four-and-a-half years at the school.

Denham's victims intermittently left in tears as the court heard how, through the protection of church colleagues, he was able to have 18 years of uninterrupted offending across schools in NSW.

At St Pius X College in the Hunter region, where he taught from 1975 to 1979, Judge Syme said the abuse happened "wherever and whenever" Denham wanted - in the playground, at his office and even outside the confessional.

With AAP.