Australia is targeting China as a potential threat as part of the AUKUS arrangement and might be breaching the UN's nuclear non-proliferation treaty via the deal.
That's according to China's ambassador to Australia Xiao Qian, who said the security pact was not a good idea and that purchasing nuclear-powered submarines was "an even worse idea".
The trilateral agreement with the United States and the United Kingdom would see Australia acquire the submarines by 2040.
"I don't think it's constructive, I don't think it's helpful, especially when you're targeting China as a potential threat or adversary," Mr Xiao told reporters in Canberra on Tuesday.
"China's not seeking to be an enemy with the United States ... there's no reason for the three countries (Australia, US and UK) to stand together to work on something that is targeting China as a threat."
Mr Xiao said it was "hard to imagine" Australia would spend so much money on a nuclear submarine using conventional weapons.
"It's not going to serve the interest of Australians, maybe it's going to serve the interest to other countries and not Australia's," he said.
He added nuclear states like the US and the UK weren't allowed to give nuclear weapons to non-nuclear states under the NPT regime, and said it set a bad example for the rest of the world.
The Department of Foreign Affairs and Trade has previously denied that claim and said AUKUS was "fully consistent with our international obligations under the NPT regime".
A statement in September called the claim "misleading" and said it contained "incorrect assertions".
Mr Xiao also touched on China's progress in the Pacific, saying relations in the region were for peaceful purposes and did not pose a threat to Australia's national interest.
"We are committed to developing our relationships (based on) ... mutual trust, economic development and co-operation, to help these countries improve their lives," he said.
"There is no military intention. There is no geopolitical intention. There is no intention to set up so-called military bases."
