A North Korean official has denied that Christians are systematically persecuted in the country, branding such accusations as "absolutely false".

In an exchange on Twitter, Alejandro Cao - the Spanish-born Special Delegate of North Korea's Committee for Cultural Relations with Foreign Countries - criticised evangelical Christians who he said "take advantage of drug addicts and homeless people and force them to become evangelists in exchange for a plate of soup".

Cao levelled his accusations at Joel Forster, the editor of online magazine Evangelical Focus, who asked him about the treatment of Christians in North Korea.

Cao became the first foreigner to work for the North Korean regime in an official capacity in 2002, and has long been an vigorous advocate of its government. Known also as Zo Sun-il - meaning Korea is one - he has been accused of threatening and intimidating journalists who criticise the country's dictatorship. In 2012, the Independent branded him North Korea's "secret weapon".

In response to Forster's question about Christians, Cao responded: "It is absolutely false. The problem in the world is that there are enlightened people like you who believe themselves to be representatives of God or even God".

In a series of follow-up tweets, he then accused Forster of being "not a religious person but an activist of the USA" and mocked the suggestion that God would bring justice to those suffering under Kim Jong Un's leadership.

"He [God] seems to be arriving late. We have been here for 70 years, and many more to come," Cao said.

North Korea is widely considered to be the worst country in which to be a Christian, and the government maintains absolute control through the systematic repression of its citizens. Around a third of North Korea's 100,000-strong Christian population are thought to be labouring in concentration camps, while tens of thousands of citizens, including many Christians, have defected to countries such as neighbouring South Korea, China, Mongolia and Russia.

The United States Commission on International Religious Freedom (USCIRF) this year said that the country "remains one of the most oppressive regimes in the world and among the worst violators of human rights."

"The government tightly controls all political and religious expression and activities, and it punishes those who question the regime," the USCIRF's 2015 report said.

"Genuine freedom of religion or belief is non-existent. Individuals secretly engaging in religious activities are subject to arrest, torture, imprisonment, and sometimes execution...While all forms of religion or belief not expressly sanctioned and operated by the state are restricted, Christians experience the most severe persecution."