WHITEHALL has launched a top-level inquiry into how a memo warning about there being too many leaks from the UK Government was itself leaked.

No 10 made clear “appropriate action” would be taken if “perpetrators are identified”.

At the weekend, it was revealed that Sir Jeremy Heywood, the Cabinet Secretary, had fired off a note to senior officials informing them that Theresa May had demanded swift action to tighten security in Whitehall.

Dated November 28 and marked "Official-Sensitive," Sir Jeremy angrily referred to a "spate of leaks and unauthorised briefings", which had appeared in the media on Brexit, the US elections and the Autumn Statement.

Asked about what was happening to get to the bottom of the leak, the Prime Minister’s spokeswoman replied: “As you would expect the usual process for leaks is being followed.”

When asked if the usual process was fit for purpose, she said: “We take this issue extremely seriously. That has been clear with the action that has been set out and will be taken in the follow-up. The civil service code sets out very clearly the role of civil servants and how they are expected to behave with regard to official information.”

Asked if the PM accepted there was a serious problem with the usual process given the memo about not leaking information was itself was leaked, the spokeswoman explained: “Action is being taken to follow up and investigate on that. That’s the position.”

Asked if Sir Jeremy’s warning applied to ministers as well, she added: “I’m not going to get into speculation who is behind the leaks or the action that will be taken in specific cases. It’s very clear there will be investigations and appropriate action taken if perpetrators are identified.”

The leak of Sir Jeremy’s memo revealed the top civil servant delivering a stern warning to colleagues. He wrote: "Leaking is corrosive and undermines trust and good government. Leaks are never acceptable but the regularity and cumulative impact of recent incidents mean we must now collectively take exceptional action."

He went on: "The Prime Minister has directed that we urgently tighten security processes and improve our response to leaks. She has instructed that we begin this work immediately and expects to see rapid and visible improvement.

"Ministers, permanent secretaries and senior officials set the tone in an organisation and no amount of process will make up for an environment where leaks are accepted. If leaders think they are the necessary cost of open ways they are mistaken."

Sir Jeremy concluded: "Anyone found to have leaked sensitive information will be dismissed even where there is no compromise of national security. The Prime Minister will be writing in similar terms to ministers."