A contentious mural on Sydney’s Bondi Beach highlighting Australia’s hardline immigration policies and deaths in detention has been vandalised, amid calls for its removal.

The black and white artwork, “Not … Welcome to Bondi”, depicted a row of heavily armed and masked Australian Border Force officers. Artist Luke Cornish, who has a show on display at the Bondi Pavilion, said the piece was a commentary on Australia’s treatment of asylum seekers.

“The 24 Australian Border Force officers represent the 24 suicides in these detention facilities (onshore and offshore) since 2010,” he wrote on Instagram recently.

The temporary mural on the seawall at the popular beach has drawn both public praise and censure, with a local Liberal councillor calling it “offensive”.

On Tuesday night the council debated a motion to have it immediately removed. That motion was defeated, with council noting it was only going to be in place for the duration of Cornish’s show anyway.

On Wednesday, however, residents discovered the mural had been largely painted over.

On Wednesday Bondi Beach residents awoke to find Luke Cornish’s mural defaced. Photograph: Dean Lewins/AAP

New South Wales police confirmed they received a report of malicious damage and are investigating the matter, while the council is reviewing footage from nearby CCTV cameras.

The Waverley Council mayor, John Wakefield, condemned the defacing of the artwork.

“The decision of council gained cross-party support for a reasoned and considered approach which took into account – and paid respect to – the artist, as well as the views of those calling for the temporary mural to be removed, and those who wanted it to remain,” he said in a statement.

“Regrettably, someone has now taken the law into their own hands.”

Local Liberal councillor Leon Goltsman had previously condemned the artwork on his Facebook page, saying it was a “failure under the Labor/Greens-controlled council”.

“What we now have are politically motivated offensive propaganda likely to offend families and turn away visitors,” he wrote on 28 July.

Travis Russell, who started a petition for the mural to be removed, told ABC Sydney radio on Wednesday he objected to the artwork because he felt it was inappropriate for the location.

“I personally feel that any depictions of guns is dangerous, and it’s [got] no place at Bondi Beach ... it is an area with a significant Jewish population, where children have to every day walk past men with guns to get into their school … the beach is an escape, and I feel it’s an inappropriate location for this kind of artwork.”

However, Russell, whose petition had almost 900 signatures on Wednesday, said he did not agree with vandals taking the matter into their own hands. He also disclosed on the radio program he was a member of the Liberal party.

A rival petition, set up by Andrew Worssam, praised the work as brave and striking and had garnered around 1,900 signatures by lunchtime Wednesday.

“It might be uncomfortable viewing for some, but that doesn’t mean it shouldn’t exist,” he wrote. “Art isn’t supposed to be hidden from sight if you don’t agree with it – that’s something totalitarian regimes do.”

NSW police are appealing for anyone who might have witnessed the mural being defaced to come forward.