Shares in the UK's largest food producer fell by more than 10% after it confirmed the departure of its chief executive.
He will be replaced by Gavin Darby, the former head of Cable and Wireless Worldwide, the company confirmed.
It comes as the firm attempts to repair its finances following a tough few years during which it almost collapsed.
While in charge, Mr Clarke was tasked with reducing the company's debts and he sold businesses including Sarson's vinegar and Branston pickle.
In November the company announced 900 job cuts at its bread business, which accounts for almost 40% of its total revenue.
Investors are concerned that the chief executive's departure could hit Premier Foods' turnaround plan.
"With its financial restructuring complete, we think that consistency and longevity of leadership was going to be critical to its prosperity."
But the company's chairman David Beever said he was "delighted" by Mr Darby's appointment, adding that his consumer goods background and management track record "make him the ideal candidate to lead the company".
Mr Darby said he was excited to be taking on the role.
"Although markets remain difficult, I look forward to working with the team to develop and grow the company's power brands in the coming years," he said.
At 4pm, shares in Premier Foods - which owns a host of well-known brands including Hovis and Oxo - were down by 10.3%.
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