Staff at a hospital accused of conducting a "witch-hunt" to identify a whistleblower felt a lack of "freedom to speak up", a report has said.
The husband of Susan Warby, who died at West Suffolk Hospital in 2018, received an anonymous letter about her care.
Bosses asked doctors for fingerprints and handwriting samples to discover the author. The trust has since apologised.
The Care Quality Commission (CQC) found the leadership "did not demonstrate an open and empowering culture".
Trust chief executive Dr Stephen Dunn said they had withdrawn the request for fingerprints in October.
"I have written to all our consultants as well as all our staff to make it clear that we have apologised," he said.
"It will now be subject to an external review and we will make sure that we learn those lessons and I am very sorry that we have impacted on staff in this way."
The hospital serves some constituents of Health Secretary Matt Hancock, who is the MP for West Suffolk, and the Department of Health and Social Care has asked the NHS to commission a review into whistleblowing at the trust.
The CQC inspection, held across September and October, rated the trust as requiring improvement, having previously been found to be outstanding in December 2017.
The regulator's report concluded hospital employees "did not feel listened to and saw others that had raised concerns be penalised".
"Not all staff felt supported, respected or valued and some feared reprisals if they raised concerns," it added.
Jon Warby said he received the letter two months after his wife's death in August 2018 and said he was "quite surprised" by the lengths the hospital reportedly went to find its author.
The report following the CQC inspection said some actions in relation to internal investigations by the hospital were "unusual and of concern".
Inspectors said some staff perceived communications as "threatening in nature, with a focus on apportioning blame".
In September, the hospital's medical staff committee raised concerns "by multiple departments in regard to the culture and behaviours of the executive body, on multiple occasions, that had not endorsed the trust values of freedom to speak up".
A meeting took place to address concerns but the CQC found that a letter to the committee's chair "could be considered intimidating, and confirmed to us the continued disconnect around communication".
Inspectors also found "significant concerns" within the maternity and midwifery service, which included the failure to track and score observations of some women and newborn babies.
The CQC put a warning notice in place stating improvements to the service must be made by 31 January.
Chair of the West Suffolk NHS Trust Sheila Childerhouse said it would be "reviewing our culture and openness to make sure there is an environment where everyone has an opportunity to contribute and play a full part in our improvement".
Mr Dunn said: "While we acknowledge and accept the areas of concern this report highlights, the CQC has rated many of the trust's services as good or outstanding and found that NHS teams across the board treated patients with compassion and respect, and we're pleased our hardworking staff have been recognised."