Former deputy chair Mike Higgins said that disagreements over the resignation of previous chair Martin Watts made it “impossible” for him to continue.
A Unison representative said the trust’s leadership seemed to be “a disorganised shambles”.
On his appointment as chair of the acute trust, Higgins said he hoped “to offer stability and focus”.
However, two days later he was explaining his own resignation: “The non-executive board members want to understand the process and detailed timeline related to the complaints and ultimate resignation of the previous chairman.
“While this was agreed to, there was strong resistance from the executive team to provide full disclosure of the timeline of events.”
The NHS Trust Development Authority (TDA) said that an independent investigation had upheld a complaint against Watts from two trust employees.
It added that it would work with the trust to provide “the leadership it needs as quickly as possible” in order to achieve Foundation Trust status.
Watts has denied the charges brought against him, details of which have not been made public.
Stuart Roden of Unison commented: “What the staff want to be doing is getting on with providing patient care, not to be seeing what almost appears to be a disorganised shambles at the top of the organisation.”