Gwent PCC Ian Johnston has told the local panel that oversees him that "Gwent Police is in a better place without the Chief Constable".
He said he gave feedback to Carmel Napier in weekly meetings, but "you can only try so many times."
"We have the evidence ready if we go to judicial review."
Earlier this month, the Police and Crime Commissioner admitted he told her to retire or be removed from her post.
Police and Crime Panels were set up alongside the Police and Crime Commissioners last November - to oversee and scrutinise the PCCs. In Gwent, it is made up of local councillors and two independent co-opted members.
The panel is today "seeking further information" from Mr Johnston about Mrs Napier's exit.
More top news
Some bright spells this afternoon, with outbreaks of rain. Top temperature 15°C.
It's judgement day at the Millennium Stadium as Cardiff Blues take on the Ospreys and the Newport Gwent Dragons face the Scarlets.
Showers expected throughout the day especially in the north. Drier and brighter elsewhere but cooler than in recent days.