North Korea is currently on the way to developing ballistic missiles which could strike London, the Defence Secretary said as he branded the country a "massive threat".
During a period of heightened nuclear tensions arising from North Korea's military tests, Gavin Williamson also said the country is a "real danger" to Britain.
With US President Donald Trump making clear that America is ready to deal with North Korea if necessary, pressed on whether the UK is also making preparations, Mr Williamson said Britain has to "step up".
"North Korea is a massive threat, they're a real danger to this country," he told the Evening Standard.
"They are currently on the pathway to have ballistic missiles that could strike London.
"This isn't just a problem for the United States, this is a global problem. Britain has to step up in terms of dealing with it, there are threats emerging right around the world.
"Britain is global player, it is a world player.
"We will never hesitate to deal with aggression and threats, and that is what we have been known for doing in the past and that is what we continue to do."
On Monday, Mr Trump unveiled a new US national security strategy which includes strengthening the country's cyber defence capabilities, and highlighted the threats of "rogue regimes" like North Korea.
The US has also publicly blamed the country for the WannaCry cyber attack which hit the NHS and networks around the world.
The president's homeland security adviser, Tom Bossert, wrote in the Wall Street Journal that they were "directly responsible" for the ransomware attack.
Kim Jong Un's regime has, in recent months, carried out several increasingly sophisticated nuclear tests.
It has also expanded its missile programme to include weapons allegedly capable of striking parts of the US.
Mr Trump has previously ridiculed Mr Kim as Rocket Man and has warned North Korea he will take all measures needed to stop the programme.
Former chief whip Mr Williamson said the UK is working with our allies and is "always planning for the worst and hoping for the best".
"We have got HMS Argyll, HMS Sutherland going up to the region to do operations with our allies; that is something I am very proud that we are doing and we are going to continue to do," he added.
When pressed on whether there is an evacuation plan in place for British citizens in the South Korean capital of Seoul, Mr Williamson declined to answer, stating that he would not go into "operational issues".