Philip Gardner, who's advised US and UK politicians, was speaking after North Korea launched its fifth and biggest nuclear warhead, causing a 5.3 magnitude earthquake.
The United Nations Security Council scheduled an emergency, closed-door meeting after the development. Each member roundly condemned the nuclear test, including Russia and China - allies of North Korea.
Mr Gardner has said because North Korea relies so heavily on China for manufacturing and energy, the country has significant bargaining chips in terms of influencing the country's behaviour.
North Korea, led by Kim Jong-un (above), is already under heavy sanctions.
It is said the country is testing nuclear warheads in retaliation to alleged aggression from the United States.
Speaking on Premier's News Hour, Philip Gardner said: "People should really be worried about the situation of the North Korean people, utterly crushed in terms of freedom of expression, freedom of religion, freedom of thought, democracy and human rights, for decades under the Kim family.
"The United States, the United Kingdom, [and] France having these nuclear weapons as a matter of last resort is completely different to the most grotesque abuser of human rights the world has ever known, using them to terrify the rest of the Korean Peninsula."
The Foreign Secretary Boris Johnson said: "These reports are of grave concern.
"The United Kingdom strongly condemns North Korea for conducting a further nuclear test, which is a flagrant violation of UN Security Council Resolutions and a threat to regional peace and stability.
"Together with the Australian foreign minister I have spoken this morning to the Japanese foreign minister, and the UK will be consulting other international partners on a robust response."
Listen to Premier's Hannah Tooley speaking to Philip Gardner on the News Hour:
