British Prime Minister Theresa May is prepared to use nuclear weapons in a first strike attack, her defense secretary Michael Fallon warned.
His comments came during an interview on Britain's "Today" program on BBC Radio 4.
Asked under what circumstance Britain would use nuclear weapons, Fallon replied: "In the most extreme circumstances, we've made it very clear that you can't rule out the use of nuclear weapons as a first strike."
He declined to speculate on what type of situation would spark a first strike attack by Britain.
"They are better not specified or described, which would only give comfort to our enemies and make the deterrent less credible," he said.
"The whole point about the deterrent is you've got to leave uncertainty in the mind of anybody who might be thinking of using weapons against this country.
"We use the deterrent every single day. That's what it does. It deters day and night. Every single day of every single year. We have a nuclear submarine out there as our deterrent, as our protection. "
Fallon came under criticism for his remarks, the International Business Times reported.
"If we are to work towards a nuclear free world then we won't get there by politicians talking about nuclear war and providing an excuse and a blank check for every other country that seeks nuclear proliferation," said Andrew Smith of the Campaign Against Arms Trade.