A Melbourne Muslim religious leader has criticised the Prime Minister after he urged Imams to report people who try to radicalise young men in their communities.

The spiritual leader of the Hume Islamic Youth Centre, which Bourke St terrorist Hassan Khalif Shire Ali attended, has questioned what authorities did to stop Shire Ali, who had been known to federal police.

“This person was on the watch list. So what did they do? Nothing,” Mohammed Omran told The Australian on Tuesday.

“This bloody Prime Minister, instead of turning the heat on somebody else, he should answer us about what he did.

“He has spent billions of dollars – billions – on security service. And what is the end result? We have crazy people in the street.”

Prime Minister Scott Morrison on Monday urged imams to watch out for “infiltrators” and “shady characters” in mosques who preyed on vulnerable young men, and said Imams “can’t look the other way”.

Somalia-born Shire Ali, 30, fatally stabbed Melbourne restaurateur Sisto Malaspina and injured two others on Friday after driving a ute into Bourke St and setting it alight.

He was shot by an officer and later died in hospital.

Shire Ali’s family said he had mental health issues for years, had refused help and was deteriorating before he was shot dead in the attack.

But Mr Morrison rejected this as an “lame excuse” saying he was a terrorist extremist who had been radicalised.

“My encouragement to the Muslim religious communities across Australia is to raise the level of awareness and alertness,” he said.

Shire Ali was known to federal police and had his passport cancelled in 2015 amid concerns he planned to travel to Syria to fight with Islamic State.

The federal government says 14 potential terror attacks have been thwarted in recent and that 400 people are on a terrorist watch list.