The widow of the late Welsh government minister Carl Sargeant has described her agony at still not understanding the circumstances surrounding her husband’s death nine months ago.

Bernie Sargeant told the Guardian she owed it to her husband to establish the chain of events that led to him killing himself four days after being sacked by the Welsh first minister following allegations about his behaviour towards women.

Sargeant said she was seeking a judicial review into how an independent inquiry into her husband’s death would operate because she and other relatives were concerned they would not be allowed to attend and their legal team would not get the chance to cross-examine witnesses.

Speaking publicly for the first time since her husband died in November, Sargeant said: “I’m so disappointed that I have been forced to take this action. I had thought after Carl’s death that I, and my young family, would be treated with honesty and respect. Yet, we can’t help but feeling we are looking at a cover-up.

“It’s been over nine months since Carl’s death and we’re no further forward in getting answers than we were last November. All I want is to understand and process why my husband is no longer here. This whole thing just adds agony to heartbreak, but I owe it to Carl to get the full picture.”

The inquiry is being led by the barrister Paul Bowen QC but Sargeant is challenging the legality of how it will operate. Her lawyers have lodged an application for a judicial review at the high court to challenge four decisions:

To bar the family’s lawyers from being able to question witnesses.

To allow the independent investigator to bar the family from hearings.

To prevent oral evidence from being heard in public.

To prevent the independent investigator from being able to order witnesses to give evidence.

The operational protocol has been established by the permanent secretary to the Welsh government, Shan Morgan. Sargeant’s family has not suggested Morgan is not impartial but pointed out that the nature of her job meant she had a close working relationship with politicians.

Sargeant said: “We have a right to be able to hear and challenge the evidence. Please believe me, we are not trying to be obstructive, we just want to get to the truth and feel that we have a great deal to offer the inquiry. We don’t want to be excluded.”

Carl Sargeant killed himself after being sacked as communities and children secretary by Carwyn Jones, the first minister. It is understood Sargeant was facing harassment allegations from three women, which he had denied.

Family and friends claimed Sargeant was let down by Jones and Welsh Labour. After intense pressure, Jones announced an inquiry would take place into how the sacking was handled.

Sargeant’s son Jack, who subsequently won his father’s seat in the Welsh assembly, said the family and wider community were frustrated at how the inquiry had been set up. “Some of us still haven’t been able to start to grieve,” he told the Guardian. “This is an extra added stress that could and should be avoided. We’re going through enough as it is.”

Jack Sargeant said that if a judicial review was granted it would inevitably delay the start of the inquiry, which the family did not want. He said that, instead, the first minister could intervene and call for the family to be allowed to attend hearings and to cross-examine witnesses. “That would be a way of stopping further delays, which none of us want,” he said.

Hearings are expected to begin in the autumn.

Bernie Sargeant’s solicitor, Neil Hudgell, said: “I have repeatedly outlined the family’s and our own concerns to the first minister, the permanent secretary and the inquiry chair, but they have been ignored.

“Aside from the ongoing and very obvious distress this is causing Bernie and her family, we now have no other option but to seek a judicial review.”

The firm has instructed Leslie Thomas QC of Garden Court Chambers and Sheryn Omeri of Cloisters Chambers.

A spokesman for the first minister said: “This is not, and was never intended to be, a public inquiry. Nor is it an investigation into the tragic death of Carl Sargeant. That is a matter for the inquest, which is expected to take place in the autumn.

“The first minister established this investigation voluntarily, solely and specifically to give independent scrutiny of the actions and decisions which he took in relation to Carl Sargeant at the time of the ministerial reshuffle last November. Independence is assured by the appointment of a QC who will have access to all the evidence and will have the opportunity to cross-examine the first minister and other witnesses.

“The process is also designed to protect the confidentiality of the women who had made complaints about the behaviour of Carl Sargeant when he was a minister in the Welsh government. The women made those complaints confidentially and have an ongoing legal entitlement to anonymity.

“The family has been a part of the process from the outset and agreed the appointment of the QC who is leading the independent investigation. The nature of the investigation has been clear since January when draft operational arrangements for the investigation were shared with members of the Welsh assembly. The specific features of the protocol now being challenged would be wholly inconsistent with what has been established. We believe, and have consistently stated, that this proposed action cannot be justified.”