Some of Australia’s biggest stars will wear blue ribbons to the country’s top film and TV awards night as they call for all asylum-seeker children detained on Nauru to be brought to Australia.

Sam Neill, Asher Keddie, Simon Baker and Jackie Weaver are among more than 700 arts industry professionals who have signed an open letter that will be presented to the prime minister, Scott Morrison, and the opposition leader, Bill Shorten, on Monday.

“Together we send this message to parliament, to you who represent us: Please put aside parties and politics,” the letter says. “After five years of indefinite detention, we must bring these human beings to safety and ensure they receive the medical treatment they need.”

Their move comes as the independent MP Kerryn Phelps pushes a bill that would force the Morrison government to remove all children and their families from offshore detention. Phelps has been backed by the crossbench, but would need the support of one Coalition MP and Labor for the bill to pass despite the Morrison government having lost its majority.

The group of arts industry professionals, who have rallied behind the #BlueForManusandNauru campaign, are calling on the parliament to back Phelps’s bill, but they also say all “people held in the offshore detention centres on Nauru and Manus need to be brought to safety”.

In a sign of solidarity with asylum seekers in Australia’s offshore detention centres, they will wear blue ribbons to the Aacta (Australian Academy of Cinema and Television Arts) awards awards in Sydney on Wednesday night.

Neill also appears in a video message condemning the government’s immigration policies alongside entertainers such as Jimmy Barnes, Warwick Thornton and Rebecca Gibney.

“It is hard to think of anything more cruel than indefinite detention, no charges, no prospect of release, no end in sight,” Neill says. “This is barbarity.”

Barnes urges those in Canberra to put aside politics and “listen to your consciences”.

Over the past few months, the government has been transferring dozens of children from Nauru to Australia for medical treatment, sometimes as a result of a court order. In some cases, the children are being held in alternative detention venues such as hotels, serviced apartments and hospitals.

Publicly, Morrison and the home affairs minister, Peter Dutton, have maintained that Australia’s border protection policies remain unchanged.

Guardian Australia has also reported that some detainees on Manus Island have been moved to Nauru amid a worsening mental health crisis there. Late last month, a report found that refugees were increasingly being driven to self-harm and suicide by the continuing miserable conditions of Australia’s offshore immigration.

Some reports have suggested that there are now fewer than 10 asylum-seeker children left on Nauru.

Phelps said this week she would introduce her bill into the lower house on 3 December.