Premier Foods is in talks to sell its Ambrosia brand as the group announced that its chief executive, Gavin Darby, is to leave the company in January, months after a spat with activist investors.

The company behind brands including Oxo and Angel Delight also revealed it was stockpiling ingredients in order to protect the company against the risk of delays at ports should the UK crash out of the EU next March without a deal.

Darby said the firm was ramping up its stocks of imported goods such as dried egg powder and packaging to ensure a consistent supply of its products. The move could cost the firm £10m in working capital over the next few months, which it expects would be reversed “as the situation normalises”.

“In the absence of certainty over the arrangements for the UK’s departure from the EU, the group shortly intends to start a process of building stocks of raw materials to protect the company against the risk of delays at ports,” the firm said.

The foods group said it was “in discussions with a number of interested parties” about the sale of Ambrosia, its custard and rice pudding brand originally created in 1971 in Lifton, Devon, and still manufactured there today with about 300 employees. Ambrosia accounts for about 10% of group revenues, with annual sales of the brand of about £80m.

Premier said a sale of Ambrosia would allow the firm to focus on its growing brands, such as Batchelors and Mr Kipling, and to accelerate the rate at which it pays down its £510m debt.

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Darby said the decision had been made to sell Ambrosia rather than an alternative brand, partly because it was a standalone factory and therefore easier to detach from the rest of the business.

Darby, who received a £1.2m pay package last year, has been chief executive for six years. He said he would step down on 31 January as the company took on a new strategy. “The board has determined that it should focus resources on areas of the business which have the best potential for growth through accelerated investment in consumer marketing and high-return capital projects,” he said.

In July Darby faced a shareholder revolt after 41% failed to back his re-election. At a stormy annual meeting, the activist shareholder Oasis Management called on Darby to step down regardless of the outcome of the vote, accusing him of driving Premier into a “zombie-like state” because of his failure to drive growth.

Darby, however, secured the backing of a majority of shareholders and the board.

The company announced his departure alongside the firm’s first-half results. Pretax losses in the six months to 29 September widened to £2.2m from £1.2m in the same period a year earlier.

Revenue rose 1.3% to £358m, boosted by the relaunch of the Mr Kipling cakes brand and by growing demand for Premier’s Batchelors convenience pots range, as it rolls out snacking options across its brands.

Premier Foods said Mr Kipling had a “storming” first half, with revenue up 13% after a revamp that included an updated brand logo, improved packaging and TV advertising, as well as new product development such as Unicorn and Flamingo slices.

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Darby said food brands had largely been protected from a wider slowdown in consumer spending. He said the UK was at an unusual point in the economic cycle, with record levels of employment but weakening consumer confidence.

“Typically, when consumers feel more cautious and confidence is low, people eat out a little less and eat at home a little more. It tends to be good for the grocery business,” he said.

He added that wage growth was now beginning to outpace inflation, reversing the previous trend, and purchasing power for consumers had strengthened.