Kerry McCarthy, the former shadow environment secretary, resigned from the shadow cabinet in protest at Mr Corbyn’s leadership.
The MP for Bristol East has now shed light on her time in the job.
In a blog post for The Huffington Post, Ms McCarthy said her concerns about Mr Corbyn’s leadership “steadily grew” as she attended shadow cabinet meetings where the Labour leader “tended to read from a prepared script, didn’t respond to our questions, and didn’t convey any sense of strategic direction or leadership”.
She said she had little contact with Mr Corbyn’s office during the time when she was in charge of the shadow Department for Environment, Food and Rural Affairs portfolio.
But when the Leader of the Opposition’s office did engage with a Defra issue “they didn’t talk to the shadow team” while letters sent to Mr Corbyn relating to environmental issues would be passed on for a reply “months” after they had arrived.
“His office was clearly under-staffed and in a bit of a muddle,” she said.
Ms McCarthy also suggested her confidence in Mr Corbyn was shaken by certain comments made by the Labour leader.
For example, she said Mr Corbyn told a meeting of the Parliamentary Labour Party (PLP) that vulnerable people “were being forced to borrow money from hedge funds” which prompted her to wonder if he knew the difference “between loan sharks and hedge funds”.
Another example given by Ms McCarthy suggests Mr Corbyn failed to understand the Article 50 process for the UK to leave the European Union in the wake of the Brexit vote.
She said he told a PLP hustings event that “we have two years in which to trigger Article 50”.
The two-year period in the Article relates to the amount of time allowed for negotiations to take place between the two sides once it has been invoked.
She said: “That lack of grasp, when he’d presumably been prepping for such a question, bothers me.”