The country's most senior military officers were recently summoned to the Ministry of Defence (MoD) for a "non-negotiable meeting" and a "dressing down" after a recent stream of leaks to the media giving details about planned defence cuts.
Sky News understands that Stephen Lovegrove, the permanent secretary in the MoD, has been forced to make the warning on two occasions in recent weeks.
Five separate sources have independently confirmed the events. One described it as a "chest-poking", although another said it "didn't quite go as far as a b*********".
A series of leaks since the summer have revealed private proposals for cuts as the MoD finds ways to save money.
Among the more notable leaks has been news that the Royal Marines might be reduced by 1,000 personnel; a possibility that the UK's two amphibious ships might be scrapped early; and the threat of selling 28 Wildcat helicopters.
The leaks have exposed divisions between the Army, Navy and RAF as each tries to limit the impact on its service.
It is understood there was even a plan to suspend the high-level Armed Forces Committee, attended by the top military personnel and MoD officials, as a desperate attempt to plug the hole.
A defence insider said: "There was too much stuff going around that could only have come from this small group of people."
The leaks included "levels of detail and private conversations that shouldn't have been made public".
"No one is accusing the chiefs themselves of leaking but there are suggestions that some of the detail has found its way to the media via proxies," the insider added.
In the end, the suspension of the Armed Forces Committee never went ahead because Sir Michael Fallon left office suddenly following revelations about his behaviour.
Instead, the permanent secretary ended up taking the meeting in his office on the fifth floor of the MoD because Sir Michael was downstairs resigning at the time.
It is understood the five most senior officers in the Armed Forces were present: General Sir Nick Carter, the head of the Army; General Sir Chris Deverell, who is commander of the Joint Forces Command; Air Marshal Sir Stephen Hillier, the Chief of the Air Staff; and Admiral Sir Philip Jones, the First Sea Lord.
A third source familiar with the warnings admitted they were "probably quite a sensible thing to do".
Mark Sedwill is the national security adviser - he has been asked by Theresa May to carry out a review of national security following the summer terror attacks and resurging threat from Russia.
Although the review is strategic in name, it is widely feared to be an excuse for more cuts to the Armed Forces.
Asked if the leaks were effective in helping prevent cuts, though, the source replied: "Imagine what the national security adviser is making of all this? He must see a homogeneous bunch of public schoolboys just trying to get attention.
"This isn't the way to fight our corner and make our case. Sedwill will be thinking, 'What resonates with an ex-home secretary Prime Minister - more tanks to be possibly used in some far off World War III, or cyber, the threat of now and device of modern warfare?'"
A few weeks after the initial meeting, Stephen Lovegrove was forced to write a letter reiterating his warning after further leaks to the media.
According to one individual who has seen the letter, the permanent secretary re-emphasised the need for trust and warned that there could be an impact on the way the services work together if further leaks appear in the media.
It will not be popular that news of this letter has subsequently been leaked to Sky News but Number 10 was reportedly keen that action was taken to stop the briefings.
Sky News has been told: "There was anger in Downing Street, the PM wasn't happy."
"Various services have spent so long at war with each other that they have left their flank open to seeing resources and money handed over to Mark Sedwill and his growing empire."
The MoD says it refuses to comment on private meetings.