Norway's police could have prevented the bombing of central Oslo and caught mass killer Anders Behring Breivik faster, an official report says.
The independent inquiry says his subsequent shooting spree on Utoeya Island could have been halted earlier.
Breivik has admitted killing 77 people and wounding more than 240 others when he bombed central Oslo and then opened fire at a youth camp on Utoeya.
The police have been criticised for taking too long to reach the island.
A verdict in Breivik's trial is due on 24 August. He claimed he was trying to stop Muslims from taking over Norway.
The inquiry, headed by lawyer Alexandra Bech Gjoerv, came up with 31 recommendations but most damning were its findings that
The attack on the government complex in Oslo could have been prevented by effective implementation of security measures that were already in place
A more rapid police operation to protect people on Utoeya Island was a realistic possibility and the gunman could have been stopped earlier on 22 July
More security and emergency measures to prevent further attacks and "mitigate adverse effects" should have been implemented on 22 July
Presenting the 482-page report, the inquiry team questioned why the street running outside the prime minister's office, Grubbegata, was not closed to traffic as recommended seven years before.
The report also gives details of a phone-call made by a pedestrian 10 minutes after the Oslo bomb went off, giving police a good description of a man carrying a pistol and wearing protective clothing.
The operator passed the message on but the tip-off was not followed up for some two hours, the report says.
Although it was clear that a terrorist attack had been carried out, the inquiry says no immediate nationwide alert was given, no roadblocks or observation posts were set up, no attempt was made to mobilise helicopters nor did the operation centre take up offers from neighbouring police districts.
In the aftermath of the attacks, the police were criticised for their failure to use a helicopter once alerted to the shootings, and for the bungled attempt to reach the island on an inflatable boat.
That criticism is echoed by the commission, which says it took police an "unacceptable" 35 minutes to get from the lake shore to the island.
As early as 17:25 local time, shootings were reported on Utoeya. The first local police patrol arrived 30 minutes later, the report says, but the two officers did not try to find a civilian boat to travel to the island immediately.
An 11-strong elite Delta force team from Oslo arrived 14 minutes later, according to the inquiry. But they were forced to abandon their own overloaded dinghy for two civilian boats.
The intelligence co-operation between the police and other security bodies is also under scrutiny. Many Norwegians have asked why the police failed to monitor Breivik's activities before the attacks.
Most of the dead were young activists who were taking part in a summer camp on Utoeya run by the governing Labour Party.
The special commission said that although Norway's domestic intelligence agency, the PST, could have become aware of Breivik before 22 July, it did not contend that the service "could and should have stopped the attacks".
There was also praise for the government's communication with the public and the report said it was satisfied that health services had responded effectively.
Norwegian Prime Minister Jens Stoltenberg said that the commission's report could not change what had happened but it was "important because it gives us facts and knowledge - an understanding of what happened".
The attacks, regarded as the worst act of violence in Norway since World War II, sparked a national debate about the nature of tolerance and democracy in the country.
The panel of five trial judges will have to rule on Breivik's sanity when they deliver their verdict.
Their conclusion will determine whether he is given a long prison sentence or is sent to a secure psychiatric ward.
Breivik's 10-week trial was marked by harrowing testimony from witnesses about his shootings. Some victims were shot in the head at point-blank range. In the meticulously planned attack, Breivik wore a fake police uniform and methodically hunted down victims on the island.
He refused to plead guilty, evoking the "principle of necessity". He accused the Labour Party of promoting multiculturalism and endangering Norway's identity.