Mass killer Anders Breivik could have been stopped earlier and the authorities "failed" to protect the 69 young people killed on Utoya Island, according to an official report.
An independent inquiry into the shootings last July has found both the attack on the government complex "could have been prevented" and Breivik could have been "stopped earlier."
"Faster police action was actually possible. The perpetrator could have been stopped earlier on 22 July," it says.
The right-wing extremist placed a bomb in a square in Oslo before heading to the Utoya teenage activist island camp, where he then executed 69 people as they fled.
Breivik, who admits killing 77 people, many of them teenagers, is currently awaiting the outcome of a trial to determine his sanity.
Breivik, who is militantly anti-Islamic, insists that he is sane and says his killings were politically motivated.
In the commission's report, which will be presented to Norway's prime minister Jens Stoltenberg, they warn the country to prepare better.
"22 July was chaotic, dramatic and confusing, and great uncertainty prevailed. Crisis management implies demanding decision-making situations. When time is of the essence and many things are happening at the same time, one is rarely better than one's preparations."
The verdict on Breivik should be delivered on 24 August.