hen a coroner ruled this month that the Treasury "materially contributed" to Chloe Moffat's death, her parents breathed out in bittersweet relief. For a year, David and Anne Moffat had been forced to become detectives in the worst case any parent could have to solve: why their daughter took her own life.

Chloe, 26, went to her job as a personal assistant at the Treasury on a Monday last May "happy as Larry" after a weekend she'd told her friends was a "10 out of 10". She was planning a holiday with her sister, Alice, and arranging for friends to come for a dinner party the next weekend. She was, according to her father, living "the best life".

That afternoon, however, she was sent to a surprise disciplinary meeting with her manager and her manager's manager, which the coroner found left her distressed and convinced she was going to lose her job. The following morning, Chloe was dead.

Anne, 64, who is retired and used to work as the head of care at a children's hospice, said: "When she first did it, we had to question Chloe. We had to question what might have driven Chloe to this." She paused, and David added: "Criminality? Fraud? All sorts of things. Because why would somebody take their own life if they were the person that we expected?"

Anne interjected: "Are they on drugs? Are they in debt? Everything. And so we searched and questioned our own daughter."

None of this was the case. After trawling through emails, talking to Chloe's friends and colleagues and holding the Treasury to account in a gruelling, multi-day coroner's court hearing, they found out their daughter had been mistreated by her employer.

"After our investigations, it was clear it was literally that one-to-one meeting," Anne said. "Chloe never recovered. She walked out of that meeting absolutely destroyed and never recovered and went down a black hole."

Speaking from their house in the French Alps, which they bought to be near Alice, who lives there and recently had a daughter, the couple seem exhausted. If the Moffats had not fought their daughter's case, it is likely the coroner would have explained Chloe's death with one word: suicide. Instead, she made a narrative finding, explaining the circumstances that led up to the death and laying blame partly at the Treasury's door.

Since that finding two weeks ago, the Moffats have had no contact from the Treasury to offer condolences or an apology. "Now that the inquest has said that the coroner has found them responsible for Chloe's death, we would have expected for them to have written to us," David said.

Chloe was described as cheerful, popular and funny, and a person who took her job seriously. "I think Chloe was always looking to serve," David said. Anne added: "I didn't realise, but people like Chloe, who are bright, confident perfectionists, when they're given a piece of shocking news such as they might lose their job, can be very vulnerable."

The young woman was blindsided after being presented with anonymous complaints that she had shared confidential information at work, which she denied. She was not reassured that her job was safe even though she was unlikely to be dismissed, or offered a third party in the meeting to give her support or advice.

"If Chloe had known that it shouldn't have happened, if she'd known her rights, she could have walked in and said: 'I'm not having this meeting', and walked out. But of course she didn't. She didn't know that, she was a people pleaser," David said.

The coroner found Chloe was denied her rights at work, such as being told what the likely outcome of the disciplinary process would have been, which was a written warning, and that she could bring a supporter with her. Instead, she felt ambushed and was convinced she would lose the job she had worked so hard for.

Anne said: "I don't know about the original complaints about Chloe, if they were malicious or to bring her down a peg or two – she was a big personality in the office."

Her parents are considering suing the Treasury for wrongful death, particularly as they have had no response from the ministry since the finding. "If that's the only way we're going to get recognition, it's a possibility," David said.

The Treasury is obliged to give the coroner a response to the prevention of future deaths report she issued to the civil service. The coroner found there was a risk of further deaths at the Treasury because of how the department handled disciplinary cases.

The department brought a team of lawyers to the inquest, who pushed for Chloe's death to be recorded as an unexplained suicide.

"We definitely want to be in touch with the Treasury because we do want Chloe remembered for the Chloe that she was," Anne said. "And be that a bench in her name or whatever, but we want her to be remembered, but we do fear that she is going to be brushed under the carpet and lessons will not be learned."

Unusually for an inquest, the small, drab room in Surrey was full of young people in their early to mid-20s – Chloe's friends and colleagues, who wept throughout. Those who attended from the Treasury were not given bereavement leave to attend the inquest into their friend's death. "They didn't get any time off from the Treasury or support for that horrible ordeal they had gone through," Anne said.

The couple said they hoped the Treasury acknowledged Chloe and issued a satisfactory response to the prevention of future deaths report, so this nightmarish chapter could be closed and they could begin to grieve.

"We need to grieve. And I'm not sure that we have. I think the inquest has delayed that," Anne said.

David said: "The hole it's left in our lives is just enormous. We're only still coming to terms with that. Sometimes we don't feel we can attend family events because we've got something missing. We are a tight-knit family, we've all holidayed together. But now we don't have Chloe."

They said they hoped Chloe's case could help prevent other parents from going through the same experience. And they wanted to remember their daughter as the grinning, popular, confident, adventurous woman she was.

"We have got so many happy memories. So that's what we have to be positive about," Anne said. "I think: 'At least she didn't have cancer,' you know, and suffer. She was literally happy up until that meeting."

David said: "I think for sure we will continue to want to ensure that we spread the word of what we have learned from all this."

A Treasury spokesperson said: "Our deepest sympathies continue to be with Chloe's family, and the department continues to mourn Chloe's death.

"We are taking all concerns extremely seriously and are considering the coroner's 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."