The police watchdog has said it was "completely unacceptable" for a police finance officer to quit ahead of a disciplinary hearing.
Ann Hall was suspended following an allegation of potential gross misconduct relating to the misuse of public funds.
She was allowed to resign by Cleveland Police, despite a disciplinary hearing by the force being due to happen this month.
The decision has been criticised by the Independent Police Complaints Commission which has been carrying out a separate investigation into her conduct.
It has now vowed to go on with its own inquiry into an allegation that unauthorised payments amounting to thousands of pounds were made to an executive coaching company, and says its findings will still be published.
"I am very mindful that the public are extremely concerned when officers and staff resign or retire while under investigation, thereby escaping a misconduct sanction.
"I find it completely unacceptable that individuals take this option rather than face up to the case against them.
"The IPCC cannot prevent this happening and that is frustrating.
"The misconduct process should be seen through to conclusion - if it is not it will inevitably leave unanswered questions and erode public confidence.
"While we cannot bring this case to a misconduct conclusion now, I believe it is in the public interest for our investigation to continue and we will publish the evidence and our conclusions, so that the public can judge the actions of Ann Hall for themselves."
More top news
Sunderland's winless home run extended to 20 games on Saturday as they drew 2-2 with Millwall at the Stadium of Light.
Kerrie brings you Saturday's forecast
AC/DC co-founder and ex-guitarist Malcolm Young has died aged 64, his publicist has announced.