Scott Morrison refuses to back down to China as he once again calls for an investigation into how COVID-19 started

Prime Minister Scott Morrison has stood firm on his calls for China to be investigated over the origins of COVID-19, while also urging all nations to share a vaccine once it is found.

Mr Morrison took to a virtual stage on Saturday morning to address the 75th United Nations general assembly, praising the World Health Organisation for establishing an inquiry into the global response to coronavirus.

'There is also a clear mandate to identify the zoonotic source of the COVID-19 virus and how it was transmitted to humans,' he said in the pre-recorded speech.

'This virus has inflicted a calamity on our world and its peoples. We must do all we can to understand what happened for no other purpose than to prevent it from happening again.'

Scott Morrison said whoever finds the vaccine first should share it with the rest of the world (Pictured: University of Oxford COVID-19 vaccine trial) 

The inquiry resolution backed by 145 countries in May does not mention China, instead committing to an impartial, independent and comprehensive evaluation of the pandemic.

China eventually supported the European Union motion.

When Mr Morrison pushed for the inquiry into COVID-19, China's deputy ambassador compared Australia's support with the murder of Julius Ceasar. 

'Approximately identical to Julius Caesar in his final day when he saw Brutus approaching him. ''Et tu, Brute?'',' ambassador Wang Xining said, news.com.au reported.

'More importantly, it hurts the feelings of the Chinese people.' 

There are also claims that the origin of COVID-19 had evolved naturally due to contact with animals and humans rather than escaping a lab.   

Mr Morrison said there has to be an investigation into how COVID-19 started 

Australian Prime Minister Scott Morrison tours the Astra Zeneca laboratories in Macquarie Park, Sydney, Wednesday, August 19, 2020

Ties between the two nations have since been fraught, with tariffs being imposed on some goods and Australian journalists being evacuated from China.

Mr Morrison urged other leaders to share a coronavirus vaccine if they discover one.

He has previously said if Australia found a vaccine, it would be shared across the world.

'This is a global responsibility and it's a moral responsibility for a vaccine to be shared far and wide,' Mr Morrison said.

'Some might see short term advantage or even profit.

'But I assure you to anyone who may think along those lines, humanity will have a very long memory and be a very, very severe judge.'

Mr Morrison's speech also focused on the dangers of disinformation, urging for more to be done to prevent it.

'Disinformation costs lives and creates a climate of fear and division,' he said.

'It goes against Australia's values and beliefs as a free, open society.'

The University of Oxford samples from coronavirus vaccine trials are handled inside the Oxford Vaccine Group laboratory in Oxford, England Thursday June 25

The prime minister also touched on trade rules and the need to peacefully resolve disputes through dialogue.

'As an outward-looking, sovereign, trading nation, Australia also values the rules and institutions that enable international trade,' Mr Morrison said.

'We know that trade creates wealth and brings nations together. It makes us more prosperous, all of us.

'We won't retreat into the downward spiral of protectionism in Australia.'

Mr Morrison says Australia is leading efforts to reform the World Trade Organisation to create non-discriminatory trade rules as well as a digital guide.

'We need to make sure these standards serve all countries rather than any single power and that they are developed in line with the fundamental principles of the global order.'

On reform of the UN itself, Mr Morrison said Australia wanted to see multilateral institutions deliver 'for us and all nations'.

'We're committed to ensuring they are fit for purpose, that they're effective, that they're open and transparent and, most importantly, that they are accountable to the sovereign states that form them.'