OSLO, Norway—Norwegian Prime Minister Jens Stoltenberg is facing pressure to resign after a report scolded public authorities for failing to prevent or interrupt bomb and gun attacks that killed 77 people last year.

One of Norway’s largest newspapers, VG, on Tuesday urged Stoltenberg to step down, saying he bore the ultimate responsibility for the string of failures by police and other agencies during the July 22, 2011, attacks by a right-wing extremist.

Opposition leaders called in lawmakers from their summer break to discuss the report by a commission that criticized the government for failing to protect its headquarters from the bomb and police for not stopping the ensuing shooting massacre earlier.

Anders Behring Breivik has admitted to the attacks and awaits sentencing on Aug. 24.