Holding a picture of starving children at a news conference on North Korean human rights in Seoul on Tuesday, Vollertsen showed pictures of suffering in the communist republic.
A physician from Germany, he worked in hospitals in North Korea from July 1999 to December 2000 and gained firsthand experience of terrible conditions.
He is currently based in South Korea, where he organises rescue and asylum efforts for escaping North Koreans.
Vollertsen has repeatedly criticised regional and international talks concerning Pyongyang and asks why the US inevitably focuses on nuclear weapons.
"There is only one security guarantee for the starving children in North Korea: When there is no more security for Kim Jong II.
"The only way to get rid of the nukes is to get rid of Kim Jong-Il, and the best way to do that is by creating an inner collapse of the North Korean regime started by a flood of refugees - just as in the former East Germany."
Informing North Koreans
But the activist recognises that encouraging a deluge of refugees is not popular among neighbouring countries and many North Koreans.
"They [North Koreans] do not have any access to foreign media. They do not know anything about Western societies. They are brainwashed into believing that we are all homeless, drug-addicted and depraved".
South Korean President Roh
Moo-hyun is taking a tough line
To counter this, Vollertsen has been sending as many radios as he can across the border, sometimes even by balloon.
But campaigning for three years to highlight a desperate human rights situation in North Korea has made the activist unpopular – especially in Seoul.
"Never could I have imagined that the most difficult part of creating an awareness of human rights abuses in North Korea would be to raise a voice in South Korea," he said.
"Here in Seoul, I get around 1400 hate-emails per day … my activities to help the enslaved people of the North - such as my boat people project - are sabotaged by South Korean intelligence.
"My telephone is tapped, and I have minders following me the whole day. All in all, although I'm here in Seoul, I feel like I'm in Pyongyang.
"South Korea is infiltrated by Pyongyang's agents … the main targets, besides the government … the military, the student organisations, the workers' unions and the media."
Rights issues in the South
Vollertsen has also been critical of human rights violations in South Korea as well.
"Basic civil rights, the freedom of speech and the freedom of the press are endangered by the current administration … the government of President Roh Moo-hyun is cracking down on critical journalists."
"There is only one security guarantee for the starving children in North Korea: When there is no more security for Kim Jong Il"
Dr Norbert Vollertsen,
Despite his growing unpopularity, the rights activist has no plans to leave South Korea anytime soon, although he has publicly expressed growing concerns for his security.
"I wonder if I will be expelled from South Korea, just as I was from North Korea. The irony should make me shake my head in disbelief. Instead, I redouble my small efforts on behalf of the people, the children, in the North."