A full-scale cyber attack could cripple a country within minutes, the head of military intelligence has warned.
Air Marshal Phil Osborn said the UK was in danger of "falling behind" in the face of the growing threat of cyber attack and information warfare.
In a rare public address, the Chief of Defence Intelligence said the ability for an attack to be mounted without it being immediately clear who was responsible, increased the risk of confrontation though "miscalculation".
Speaking at the Royal United Services Institute military think tank in London, he urged politicians and military commanders to be prepared to "act first" in the face of potential threats before it was too late.
"Depending on opposition capability and intent and, critically, our resilience, a full-scale cyber confrontation could have the nationally strategic crippling effects in minutes and hours," he said.
"Without change, we risk falling behind in today and tomorrow's full-spectrum confrontation. More of the same will not cut it.
"We need to compete, sometimes pro-actively, and certainly just not observe. To wait for risks to mature before action is to contemplate strategic failure.
"Our aim should be to understand first, to decide first and then, if necessary, to act first across the physical and the virtual."
Air Marshal Osborn said the military application of new technology action was having a transformative effect on the way wars were fought.
"The aggressive application of machine-learning, artificial intelligence and quantum computing to full-spectrum operations is likely to be as disruptive to modern warfare as air power was some 100 years ago," he said.
He warned that the ability to launch "hidden" attacks in cyberspace and elsewhere could embolden some potential adversaries to become more aggressive - heightening the risks of an actual conflict.
In a reference to the Salisbury nerve agent attack on former Russian spy Sergei Skripal, he said that as recently as three months ago, the possibility of a state-sponsored chemical weapons attack in an English city would have seemed "inconceivable".
"For some, this ability to wage hidden and difficult-to-attribute warfare in cyberspace and elsewhere brings the opportunity for them to be much more aggressive and to take risks," he said.
"We can see numerous examples: unprecedented industrial espionage activity against the UK and allies, private security contractors being used in high-end capability warfare in Syria, cyber attacks against national infrastructure and reputation across Europe, information operations that attempt to pervert political process and frustrate the rule of law, and attempted assassinations.
"The consequent risk of confrontation and miscalculation is rising."
Air Marshal Osborn said "deception and counter-deception" operations would be "critical" in dealing with such threats.
"We need to have a convincing justification and narrative for our actions while countering opposition disinformation and lies with the truth," he said.