US Army whistleblower Chelsea Manning will not be allowed to enter Australia for a speaking tour scheduled to start on Sunday, her tour organiser has said.

Think Inc said it had received a notice of intention from the government to deny Ms Manning entry.

“Which after a little bit of research and speaking to our legal counsel, we understand is potentially an imminent refusal of her visa,” Think Inc director Suzi Jamil told the Australian Broadcasting Corp.

The group is calling on her supporters to lobby new Immigration Minister David Coleman to allow her into Australia.

Ms Manning was an intelligence analyst for the US Army when she leaked military and diplomatic documents to the anti-secrecy website WikiLeaks.

She served seven years of a 35-year sentence before then-President Barack Obama granted her clemency in 2017.

The transgender activist, who recently lost a long-shot bid for a US Senate seat in Maryland, is scheduled to speak at the Sydney Opera House on Sunday and has subsequent events in Australia and New Zealand.

The Department of Home Affairs said while it does not comment on individual cases, all non-citizens entering Australia must meet character requirements set out in the Migration Act.

The reasons a person might fail the character test include a criminal record or a determination they might be a risk to the community, according to the department.

Labour foreign affairs spokeswoman Penny Wong said the government should be transparent about the reasons, if Ms Manning is denied entry.

By refusing her entry, the Australian government would send a chilling message that freedom of speech is not valued by our government

Claire Mallinson, Amnesty International

Amnesty International accused the government of trying to silence Ms Manning.

“By refusing her entry, the Australian government would send a chilling message that freedom of speech is not valued by our government,” the organisation’s national director Claire Mallinson said in a statement.

Lawyer Greg Barns, who has represented WikiLeaks founder Julian Assange, said people with criminal records have been allowed into Australia in the past.

He said no one would seriously suggest Ms Manning was a risk to the Australian community.

Ms Manning is also facing calls to be barred from New Zealand, with the centre-right National Party opposition urging the government to decline her visa request.

She was due to speak in the Australian city of Melbourne on September 7, the New Zealand city of Auckland on September 8, the New Zealand capital Wellington on Septembe 9 and the Australian city of Brisbane on September 11.