Lord David Alton told Premier: "I do think rhetoric on both sides, the war of words, has gotten completely out of hand.
"I think it's time that people said less and remember what Churchill said, that foolish talk can cost lives."
A former US deputy secretary of state has also warned against using "hot rhetoric" as international tensions over North Korea's missile testing continued to escalate.
The rogue state's leader Kim Jong Un has warned Donald Trump he would "pay dearly" after the US president threatened the total destruction of North Korea.
US Defence Secretary James Mattis announced "diplomatically-led" efforts to end the standoff with North Korea are continuing.
China and Britain have agreed to continue to ramp up pressure on North Korea over its nuclear weapons testing.
In a telephone call, Prime Minister Theresa May and Chinese president Xi Jinping said the two nations have a "particular responsibility" to find a diplomatic solution to the crisis.
Lord Alton told Premier that the UK government should consider if it's right to have an ambassador in North Korea if "no notice whatsoever is going to be taken of resolutions passed by the Security Council".
