The Treasury “materially contributed” to the death of Chloe Moffat, a 26-year-old personal assistant who took her own life after facing disciplinary proceedings, a coroner has found.

Anna Crawford also found there was a risk of future deaths within the civil service from flawed handling of disciplinary proceedings. She said she would send a prevention of future deaths report to the head of the civil service, the Treasury, and the Advisory, Conciliation and Arbitration Service (Acas).

Moffat had worked at the Treasury as a personal assistant for almost three years. She “loved her job” and had an “exemplary employment record”, the coroner heard during the three-day hearing.

However, she was driven to “distress” by an informal meeting about an anonymous complaint at work. It alleged she had informally shared information about colleagues which she had been privy to during her job. Moffat had denied the allegation.

During the disciplinary process, the Surrey coroners’ court heard, she was not reassured that her job was safe even though she was unlikely to be dismissed, and she was not allowed to have a third party of her choice in the meeting. She had her job responsibilities temporarily changed and her access to the diary of her manager removed. This was despite the meeting being described as “informal”.

The process left her “devastated” and convinced she had lost her job. The morning after the meeting, Moffat killed herself.

The coroner found Moffat “appeared well and happy” before the meeting on 19 May last year and that there were no previous concerns about her mental health. She said: “I am satisfied that the shock and distress of the allegations and thinking she was going to lose her job contributed to her state of mind.”

The Treasury’s human resources policy, which is in line with Acas guidelines, says that serious misconduct allegations have to be dealt with formally. This is so the person involved is “not deprived of their rights”, such as having a third party present during meetings, being given five days’ notice and being informed of the likely outcome if the allegations are found to be true, the coroner said.

She found that because decisions had already been made to limit Moffat’s role and responsibilities, the allegations “needed a formal process”. Crawford said: “I find the meeting was not in accordance with [Treasury] policy”, which “makes no provision” for such informal meetings. “The reason for this seems abundantly clear,” she added. “It is necessary to put safeguards in place, including informing about the likely penalty and the right to be accompanied.”

The head of global issues at the Treasury, who was running the investigation into Moffat, said during the coroner’s hearing that she did not give Moffat prior notice of the meeting because “she did not want Chloe to worry about it”. She had also told the court that when Moffat asked in tears whether she would lose her job, she had replied that she could not predict the outcome of any potential investigation.

Earlier in the hearing, when asked if she would have done anything differently, Moffat’s line manager told the court: “No, I think we did all we could at the time with the information and advice we were given.”

But the coroner found: “By handling the matter in the way they did, Chloe was denied safeguards.

“The concern that she would lose her job did materially contribute to her state of mind and the decision to take her own life,” Crawford said. She found the Treasury played a part in Moffat’s death by not informing her that the likely outcome would be a written warning and not dismissal.

Crawford was issuing a prevention of future deaths notice because the Treasury claimed these informal meetings were “standard practice”. “That is a matter of concern,” she said. “It runs the risk of serious and/or gross misconduct allegations being put to colleagues without safeguards in place.”

The Treasury previously said it was reviewing its disciplinary process. “This does not set my mind at rest,” the coroner said. “I consider there remains a risk of future death.”

Anne Moffat, Chloe’s mother, said: “Chloe was a bright, caring and talented young woman who loved her family, her friends and her work. The evidence heard during the inquest has reinforced our belief that the allegations made against Chloe were nothing more than workplace gossip.

“She was treated with a complete lack of empathy with regard to allegations made by colleagues who chose to remain anonymous. We continue to believe that HM Treasury failed in its duty of care towards Chloe. At a time when she needed support, reassurance and fair treatment, she was left frightened, isolated and convinced that her career and reputation had been destroyed.”

Anne Moffat suggested the family may take further action: “We will continue to honour her memory and seek the changes needed to ensure that no other family suffers a similar loss.”

A Treasury spokesperson said: “We continue to mourn Chloe’s passing as a colleague and friend. Our thoughts remain with her family and friends. We take the coroner’s concerns extremely seriously and recognise it is important to act quickly. We are now considering the findings carefully.

“We have introduced improvements to guidance, support and wellbeing arrangements but recognise we must continue to take action to prevent this happening again.”