A security guard who kidnapped a lost three-year-old girl in a shopping mall and sexually assaulted her will be deported from Australia - as it's revealed he arrived in the country illegally but was allowed to stay.

Mohammad Hassan Al Bayati, 30, touched the victim's underwear and exposed himself in a stairwell away from cameras at DFO Homebush in Sydney's west in December 2016.

The Iraqi man, who arrived to Australia by boat in 2011, will have his permanent protection visa revoked by the Department of Home Affairs.

Prime Minister Scott Morrison said Al Bayati's crime was 'appalling'.

'I was absolutely appalled and sickened,' he told Seven News on Thursday morning.

'This bloke has no right being here. He has abused the generosity of a country that gave him a new start.'

Mohammad Hassan Al Bayati (pictured), 30, touched the victims' underwear and exposed his penis in a stairwell away from cameras at DFO Homebush in Sydney's west in December 2016

Home Affairs Minister Peter Dutton has begun the formal process of stripping Al Bayati of his visa, the prime minister said.

Mr Morrison said since he was immigration minister some 4,000 refugees have been deported for committing crimes that result in a sentence longer than 12 months.

Al Bayati faced NSW District Court on Tuesday and was jailed for four-and-a-half years but will be eligible for parole in July 2021.

He was earlier in the year found guilty of kidnapping with intent to obtain sexual gratification, an act of indecency with a victim under 10 years old and indecently assaulting a person under 16.

The guard responded to a report a distressed girl was lost at the mall's playground.

He took her by the hand to the fire exit stairwell – an unmonitored area – where he indecently assaulted her as part of an 11-minute ordeal a week before Christmas.

The Iraqi man, who moved to Australia illegally by boat in 2011, will have his permanent protection visa revoked by the Department of Home Affairs

Home Affairs Minister Peter Dutton has begun the formal process of stripping Al Bayati of his visa, the publication reported (pictured: Al Bayati with the young girl before she was sexually assaulted)

Al Bayati walked the toddler back to the playground where her seven-year-old sister was crying because she couldn't find her younger sibling.

When the mother returned to her children from shopping, she was berated by Al Bayati for leaving the two girls unsupervised.

'The gall of the offender to lecture the mother about the dangers and risks of leaving her in the play area when he ended up being the greatest risk is one of the most curious parts in this matter,' Judge Pickering said in sentencing.

'Any mother should be entitled to leave their children in a busy shopping centre and not have any belief or expectation that someone who is actually there to look after the interests of people shopping in the centre will then create harm in themselves.'