The regime is also desperate to keep its death toll from the people, he said, and was terrified of the 'shockwaves' that would rock society if the real impact was known.
And the new hospital being built in Pyongyang is all part of the propaganda effort, he told the Committee for Human Rights in North Korea (HRNK).
Kim Myong, who held a senior government role in North Korea, said it was 'absurd lies' to claim the country had no coronavirus cases and the true number 'very likely... exceeds imagination'.
Myong's insight follows hard upon recent speculation leader Kim Jong-un was himself 'gravely ill' after heart surgery, rumours since dismissed as untrue by officials in South Korea.
Speculation around the North Korean leader's health began when he was absent from a celebration of his grandfather's birthday on April 15, one of the biggest events of the year.
The claim about Kim Jong-un's ill health emerged in a report for a website run by North Korean defectors on April 21.
'He [Kim Jong-Un] is afraid of the shockwaves that may reverberate through society if data were released on the loss of precious life because of lack of proper testing and treatment.'
'China has launched a disinformation campaign to dispute the Chinese origin of the virus,' Myong said.
'If North Korea transparently publicised its coronavirus figures, this could add a factcheck, potentially undermining China's denial and disinformation campaign.
'The two countries share an 880-mile-long border, and admission of a massive COVID-19 outbreak in North Korea would substantially reinforce evidence that the pandemic originated in China.
'Kim Jong-un might have decided to conceal the real data to avoid embarrassing Chinese premier Xi Jinping.
'With North Korea increasingly isolated on the world stage, China is perhaps its only ally and relations between the two nations are said to be as close as 'lips and teeth'.
In fact, it's been said that the North's economy is 'completely dependent' on China.
But Mr Kim said there were also domestic reasons to suppress the truth about the virus.
The defector said: 'In March, Kim Jong-un unexpectedly launched a project to build the Pyongyang General Hospital and appeared at the groundbreaking ceremony.
'Since then, North Korean media has been ramping up propaganda, praising his leadership and the superiority of the socialist health system.
'However, no one truly believes that propaganda any more. All of this propaganda and glorification of the leader is paradoxically an indication that Kim Jong-un has something to hide and is fearful of the wavering hearts and minds of the population.'
Pictured: The regime has brought in workers who are engaged in a 24/7 operation to build the new hospital in Pyongyang
Pictured: Construction workers in face masks busily laying new footings at the site of the so-called 'propaganda effort' hospital in Pyongyang
Mr Kim continued: 'He is afraid of the shockwaves that may reverberate through society if data were released on the loss of precious life because of lack of proper testing and treatment.
'He fears the negative impact of such information on North Korean society and its potential to alienate the population from the regime.
'The cost in human lives will not dissuade Kim Jong-un,' the defector added.
He said: 'To Kim Jong-un, letting hundreds, thousands, or even tens of thousands of North Koreans die of the disease like worthless slaves would not be an issue.
'To him, watching so many people die would be less painful than a finger prick spilling one droplet of his own blood.'
'In conclusion,' he added, 'it is very likely that the number of coronavirus cases and fatalities in North Korea exceeds imagination.'
Mr Kim said his observations were 'based on my knowledge of North Korean society and personal life experience'.
Greg Scarlatoiu, executive director of HRNK, said North Korea faced a potential disaster on the scale of the notorious famine which killed at least 240,000 people.
'The entire world is paralysed by the COVID-19 crisis,' he said. 'But we have to remember that hot spots are still out there.
'The brutal repression of human rights, the utter lack of transparency and the ruthlessness of the Kim regime may create a humanitarian crisis even worse than the Biblical famine of the 1990s.
'We must be prepared to help. We must be ready. Those of us who have the skills and knowledge to help will have to be on the frontlines.'
North Korea continues to officially deny the presence of coronavirus within its borders, with state propaganda stating earlier this week that 'there is not even one infected person in our republic'.
However unverified reports of a viral outbreak within the country have continued to leak to foreign media.
There's also rampant speculation that Kim Jong-un himself may be gravely ill or may even have died after he missed a number of high-profile events.