Theresa May ordered a crackdown on secrecy in notoriously leaky Whitehall, in part to keep tighter control over her Brexit strategy | Jack Taylor/Getty Images UK leak inquiry launched into how leaks memo was leaked Theresa May’s message that divulging information won’t be tolerated does not appear to be getting through.

The British government has launched an inquiry into how a secret memo calling for a ban on leaks to the press was leaked to the press.

Theresa May ordered a crackdown on secrecy in notoriously leaky Whitehall, in part to keep tighter control over her Brexit strategy. In a memo dated November 28 and marked "Official — Sensitive," the head of the Cabinet Office, Jeremy Heywood, told senior staff about a “spate of leaks and unauthorized briefings” that had appeared in the media.

“Leaking is corrosive and undermines trust and good government,” Heywood wrote, according to the Times. “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.”

He warned there would be "tough disciplinary measures when a culprit has been identified to show leaking will never be tolerated” and added that "anyone found to have leaked sensitive information will be dismissed, even where there is no compromise of national security."

Despite the warnings, the memo on stopping leaks was itself leaked, to the Mail on Sunday.

On Monday, the Cabinet Office launched a probe into how the memo found its way into the hands of journalists, according to the Mail.

There have been several leaks of secretive government discussions on Brexit. In October, the Guardian revealed that ministers had been warned that pulling out of the EU's customs union could lead to a 4.5 percent fall in GDP by 2030.

Also in October, the Times obtained a government document claiming that a "hard Brexit" could see the U.K. Treasury miss out on up to £66 billion a year in tax revenues.