Australian Foreign Minister Marise Payne says China's disqualification of Hong Kong lawmakers seriously undermines the city's democratic processes and institutions.
The expulsions follow the arrests of pro-democracy lawmakers in Hong Kong over an incident in the Legislative Council earlier this year.
"Australia calls on authorities to allow the Legislative Council to fulfil its role as the primary forum for popular political expression in Hong Kong," Senator Payne said on Thursday.
She described the Legislative Council as a key pillar of the rule of law and the city's "One Country, Two Systems" framework.
"This is critical to maintaining international confidence in Hong Kong," Senator Payne said.
"Australia and the international community will continue to monitor developments closely and maintain a consistent focus on human rights and the principles of freedom, transparency, autonomy and the rule of law."
Liberal MP Gladys Liu was among several federal politicians to express dismay about the latest crackdown in Hong Kong.
"I am very saddened to see a place that I was born and grew up, the democracy that I enjoyed is disappearing," Ms Liu said.
"That platform of freedom of expressing political views is taken away, and that is very sad to see."
Labor foreign affairs spokeswoman Penny Wong said the expulsions represented a further weakening of Hong Kong's democratic freedoms.
"This undermining of Hong Kong's principal forum for political participation follows an alarming pattern of suppressing opposition voices," Senator Wong said.
"Labor is deeply concerned by the continuing erosion of Hong Kong's high degree of autonomy as guaranteed in the Basic Law and the Sino-British Joint Declaration, to which China is committed."
Greens senator Janet Rice said the disqualifications were a slap in the face to the millions of pro-democracy Hong Kong residents.
"Carrie Lam has done a huge disservice to the people of Hong Kong in allowing Beijing free rein to control political dissent and quash the free exchange of ideas in the legislature," she said.
The United States says the disqualifications leave no doubt the Chinese Communist Party has flagrantly violated its international commitments and promises to the people of Hong Kong.
"One Country, Two Systems is now merely a fig leaf covering for the CCP's expanding one party dictatorship in Hong Kong," US National Security Adviser Robert O'Brien said.
He said the US would use all powers available to identify and sanction those responsible for extinguishing Hong Kong's freedom.