Without Childline the sexual abuse of a young Sligo girl would never have come to light, Mr Justice Paul Butler said at the Central Criminal Court when he jailed her father for four years.
Mr Justice Butler also praised Sergeant James Costello and his colleagues in An Garda Siochana for what he described as "their very sensitive handling" of the case.
The 33-year-old Sligo man was found guilty by a jury in July on 12 charges of sexually assaulting his now 15-year-old daughter on various dates from 1996 and 1999.
Defence counsel, Mr Anthony Sammon SC (with Ms Isobel Kennedy BL), told Mr Justice Butler his client still maintained his innocence of the charges and he was therefore unable to offer any submission in mitigation.
The jury of five women and seven men deliberated for about four hours before convicting him on day-4 of the trial. He was found not guilty by direction on two further rape charges. He had denied all the charges.
Mr Justice Butler said he regarded the offences as being very serious and on the upper end of the scale of sexual assault and noted that many people would regard the five years maximum sentence as permitted in the legislation as "ludicrous".
The young victim should have been able to trust her father and the very bad effect of his offending had caused her great trouble in her life. This situation was compounded by disbelief but the jury had fully accepted her story.
"I cannot give enough praise to Childline without which this abuse would never have come to light", said Mr Justice Butler. "I wish her the very best for the future".
Mr Justice Butler certified her father as a sex offender under the recent legislation on the application of prosecuting counsel, Mr Des Zaiden BL.
The girl told the trial in July she found it very difficult to trust people and said the first person she had been able to talk about the abuse she was going through was "the man who answered the phone" at Childline when she called them for help on October 16, 1999.
Her mother refused to testify at the trial after she was sworn in. She said: "I love them both and I do not wish to give evidence."
The court agreed to exercise Section 22 of the Criminal Justice Act 1984 which allows signed statements by witnesses to be read out to the jury and treated as sworn testimony.
The statement showed the mother worked full-time and attended weekly bingo sessions at a local venue at the time of the offences. This conformed with the victim's allegations that the incidents took place when her mother was absent from the house.
She denied in cross-examination she did not tell her mother about the allegations because they were false. Her reason for keeping it a secret from her mother, she said, was because her mother might disbelieve her.