The widow of a former Welsh government minister, who was found dead while he was facing sexual misconduct allegations, has won a high court bid to challenge the legality of an inquiry into his sacking.

Bernie Sargeant was given the go-ahead for a full judicial review hearing by a judge in London on Tuesday.

An investigation into the way her husband, Carl Sargeant, was treated by the first minister, Carwyn Jones, has been suspended pending her legal move relating to how it should proceed.

Mr Justice Supperstone granted Bernie Sargeant permission for a judicial review, ruling that she had an “arguable” case.

A full hearing of her action against the first minister is now expected to be heard in Cardiff on a date to be fixed.

Carl Sargeant, 49, was found dead at his home last November, four days after being removed from his role as cabinet secretary for communities and children amid allegations of inappropriate behaviour.

The politician, from Connah’s Quay, north Wales, was suspended from the Labour party over allegations of “unwanted attention, inappropriate touching or groping” on 3 November.

His family has said he was not told the details of what he was accused of and was unable to properly defend himself.

Carl Sargeant, formerly the cabinet secretary for communities and children. Photograph: Polly Thomas/Rex/Shutterstock

The father-of-two was found dead at his home on 7 November.

The first minister announced an independent inquiry into how he handled his former minister’s sacking.

Bernie Sargeant is challenging the legality of the operation of the inquiry, and has spoken publicly of her concerns that the investigation could become a “cover-up”. Her high court action was launched to challenge “unlawful” decision-making in relation to the investigation’s operational protocol, which will govern how it will proceed.

The decisions in question include “the barring of the family’s lawyers from being able to question witnesses”, another “to allow the independent investigator to bar the family from hearings”, and also a move to “prevent oral evidence from being heard in public”.

Nathalie Lieven QC, representing Bernie Sargeant, argued before Supperstone that the way the terms of the investigation had been set amounted to a “flagrant breach of natural justice”.

When news of the legal action was announced, Bernie 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.”

She added: “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.”

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.

“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.”

Supperstone heard an argument on Bernie Sargeant’s behalf after an earlier rejection of her case by another judge, who reviewed her application on paper.

He also heard from a QC on behalf of the first minister, contesting the application.