Claims that martial law could be introduced in the event of a no-deal Brexit have been called "complete nonsense".
The National Security Adviser Sir Mark Sedwill was responding to questions from MPs over reports that the military could be brought in to govern if Brexit chaos ensued.
“Thank you for giving me the opportunity to put on the record, the martial law story is complete nonsense,” Sir Mark told a committee of MPs.
"I genuinely have no idea where it came from, I don’t know who briefed it but it is complete nonsense.
"I’m grateful for the chance to say that," he added.
The National Security Advisor also said there is "no plan" to use the Civil Contingencies Act.
The Act was introduced in 2004 after a series of emergencies, such as the outbreak of foot-and-mouth disease in 2001.
It allows the Government to respond to a national emergency that imposes a threat to human welfare. Such a threat could mean disruption of access to food, water or energy.
In such an eventuality, military personnel would be kept on standby.
However, it is reported that 1,000 staff from the Defence Equipment and Support Agency could be transferred to other departments in the event of Britain leaving the EU on 29th March with no deal.
Earlier this month, it was confirmed that reservists in the British military could be called out on operations if there is a no-deal Brexit.
The MOD has already confirmed planning is underway for if a no-deal Brexit takes place.
A government spokesperson told the BBC:
"The civil service has the flexibility to deliver government priorities and deploy resource appropriately to do this.
"This includes departments sharing staff and working together on joint projects".