A Foreign Office whistleblower has won a case for unfair dismissal over her disclosures to the BBC about the UK evacuation from Afghanistan.

Josie Stewart revealed details of the chaotic August 2021 withdrawal from Kabul and emails which suggested then Prime Minister Boris Johnson’s had been involved in the evacuation of a pet charity.

She had her security clearance revoked and lost her job after a BBC journalist accidentally identified her as a confidential source on social media.

An employment tribunal, chaired by Judge Andrew Glennie, found she had leaked the information in the public interest and had been unfairly dismissed.

A BBC spokesperson said: “We take our responsibilities as journalists very seriously and we deeply regret that the name of the email account was inadvertently revealed when the email was published on social media.”

Lawyers for the Foreign, Commonwealth and Development Office (FCDO) said Ms Stewart’s bosses had been forced to sack Ms Stewart because her security clearance had been revoked and there were no other suitable roles for her.

But Ms Stewart’s barrister, Gavin Millar KC, said that if their argument had succeeded it would have driven “a coach and horses through” the Public Interest Disclosure Act 1998 (Pida) aimed at protecting whistleblowers.

In a judgement issued on Tuesday, the employment tribunal said Ms Stewart had been justified in going to the media on a clear matter of public interest.

“The tribunal considered that it was reasonable for the claimant [Stewart] to go to the UK’s public service broadcaster when relevant information and/or allegations had already been put into the public domain … and government ministers were publicly disputing them.”

The tribunal heard that Ms Stewart had “experienced a culture in FCDO which silences concerns and ostracises those who raise them”.

She said her experience of the FCDO’s Afghanistan crisis centre in August 2021 “reflected the worst of our political system”.

In a statement upon receiving the judgment, she added: “By calling this out, I lost my career.

“The outcome of this case doesn’t change any of this, but it has achieved what I set out to achieve: it has established that civil servants have the right not to stay silent when systemic failures put lives at risk, as happened during the Afghan evacuation.

“I hope that, knowing that their colleagues have this right, senior officials will do more to build accountability in government, and speak truth to power when it is needed.

“We can’t have a system that says stay silent, no matter what you see, and forces dedicated public servants to choose between their conscience and their career.”

Elizabeth Gardiner, chief executive of whistleblowing charity Protect, welcomed the ruling.

“We need whistleblowers to raise matters in the public interest and this case is unusual and hugely significant in finding that a civil servant was justified in going to the press.”

She added that the decision had “weighty repercussions for how civil servants can act in the future and their confidence in speaking out when they encounter wrongdoing”.

But she said it did not remove the need for better protections for civil servants who raise concerns internally through an “independent statutory commissioner”.

An FCDO spokesperson said: “We will review the findings of the tribunal and consider next steps.”

Remedies for Ms Stewart’s successful complaints will be determined at a future hearing.