Tate & Lyle has refused to say why its head of mergers, acquisitions and investor relations left the company.

Mark Robinson's exit last week has fuelled speculation over the future of chief executive Iain Ferguson, who faced criticism from shareholders over his handling of last month's 28% drop in share price. The fall came on the back of the third profit warning for Tate & Lyle in under 12 months.

Tim Lodge, financial director of Tate & Lyle's food and industrial ingredients arm, has replaced Robinson. Lodge will not be directly replaced as the department is being restructured.

The company has been trying to move away from commodities to higher value products such as its Sucralose sweetener. It has sold off its European wheat starch plants and is to sell its interest in its Mexican sugar cane business.

"These transactions represent important steps in reshaping our business to reduce the impact of our exposure to raw material and commodity markets," said Ferguson.