Damien Guerot has been praised for using a bollard to stop killer Joel Cauchi from reaching the upper levels of the Westfield Shopping Centre in Bondi Junction during the devastating rampage on April 13.

"I say this to Damien Guerot who is dealing with his visa applications, that you are welcome here, you are welcome to stay for as long as you like," the prime minister said on April 16.

"This is someone who we would welcome becoming an Australian citizen, although that would of course be a loss for France," he said.

"We thank him for his extraordinary bravery.

"It says a lot about the nature of humanity at a time when we are facing difficult issues, that someone who is not a citizen of this country stood bravely at the top of those escalators and stopped this perpetrator from getting onto another floor and potentially inflicting further carnage on citizens.

"I think that on Saturday we saw some of the best of human character at the same time as we saw such devastating tragedy.

"And I thank Damien for his extraordinary efforts."