"Apparently, no one will ever learn from the grave mistakes that were made on July 22nd, not the police nor anyone else," lamented Alf Vederhus who lost his son Haavard in Breivik's mass shooting on the island of Utøya.

The Norwegian police's internal affairs unit said in a statement on Thursday that while there were serious shortcomings in the police's response, it had dropped its investigation into complaints filed by the families of two victims because there was no evidence police had broken the law.

"I think internal affairs looked too lightly on the mistakes that were made," Vederhus told the daily Dagsavisen.

Breivik, a right-wing extremist, detonated a bomb outside the centre-left government's headquarters and then went on the rampage at a Labour Party youth camp on the island of Utøya, killing a total of 77 people, many of them teenagers.

He was in August 2012 found sane and sentenced to Norway's maximum sentence of 21 years in prison, a sentence that can be extended indefinitely if he is deemed a continued threat to society.

Breivik confessed to the attacks, calling them "cruel but necessary" to protect his country from the multiculturalism his victims embraced and which he hates.

Less than two weeks before the verdict was rendered, a commission tasked with learning lessons from the attacks harshly criticized the Norwegian authorities, saying the bombing could have been prevented and Breivik's killing spree could have been stopped earlier.