Peter Dutton’s claims of an suspicious incident involving asylum seekers and a young boy, which he said led to soldiers opening fire on the Manus Island detention centre, remain completely unsupported by evidence, the Greens senator Nick McKim has said.

McKim, who has been on Manus inspecting the living conditions for asylum seekers and refugees sent there by Australia, said multiple eyewitnesses and authorities had denied the immigration minister’s claims.

Speaking to Guardian Australia from Papua New Guinea, McKim said he had spoken to the regional police commander, David Yapu, local MP Ronny Knight and dozens of eyewitnesses to the Good Friday shooting and an event weeks earlier when a young local boy asked refugees for some food.

“What I can say is that both the PNG police and Ronny Knight, and all of the detainees … are consistent in their positions, and that is that an event involving a small child had nothing whatsoever to do with the attack and the shooting, which obviously puts the lie to Peter Dutton’s version of events,” he said.

“What happened with the child on my advice … is he went to the centre to ask for food and he was given food by detainees and by Wilsons Security staff and then he left the centre. There has been no complaint laid … to PNG police about that event.”

Dutton has repeatedly cited confidential sources to support his claim that three asylum seekers were seen leading a five-year-old boy into the centre, and speculation about their plans contributed to unrest that culminated in the shooting.

His claims have been repeatedly rejected by Yapu, Knight and refugees and asylum seekers who have called for the release of CCTV footage they say will show the boy asking for and receiving food.

Dutton has refused to release the footage publicly but apparently showed it to Sky News host Andrew Bolt. Bolt’s account of what he watched largely supported the police and asylum seekers’ accounts but he suggested it still appeared suspicious.

McKim said Yapu told him there had not been any complaint or allegation made by the family of the young boy in question.

He said multiple eyewitnesses reported seeing the boy walk through the centre with asylum seekers and security and be given food. How the boy was permitted to walk through multiple entry points at the centre was unknown but was a question for the facility’s security operator, McKim said.

Asylum seekers also supported the authorities’ account of what sparked the shooting – an incident on a football field that escalated into violence. Yapu had previously told Guardian Australia an asylum seeker allegedly assaulted a navy personnel member.

McKim said the Coalition “had form” in telling lies to “demonise refuges and people seeking asylum in the minds of the Australian people”, citing the children overboard affair. He called for Dutton to retract his comments, apologise and resign.

McKim visited Manus Island to investigate the conditions for asylum seekers and refugees sent there under Australia’s offshore processing policy.

He was not permitted entry to the facility, a decision he described as “disappointing and frustrating”.

He said the local community was not consulted before Australia and the PNG government made a deal to build the regional processing centre there. “Of course there are concerns held by the local community, but there are also other members in the community who are very glad about employment and the economic opportunity generated by the camp,” he said.

McKim said while he found a range of views in the community about the centre and its occupants, “there’s been no alternative version put to me about the Good Friday shootings”.

Dutton’s office has not responded to multiple previous requests for comment on the issue.