Synlait Milk's chief financial officer Angela Dixon has resigned, the company said.
Her resignation follows the sudden departure in mid-April of Synlait's chief executive Leon Clement.
The company's co-founder and former chief executive John Penno is filling in as CEO until a replacement is found.
In a statement today, Pennosaid: "On behalf of our team, I would like to thank Angela for her contribution and commitment to the organisation during a difficult period in Synlait's history."
Dixon had led Synlait through several market updates and delivered a successful $200 million capital raise, which Penno thanked her for.
Synlait's general manager supply chain, Rob Stowell, will step in as the interim chief financial officer.
Stowell is one of Synlait's original employees and has held a variety of roles within the business, including senior roles in the finance team, Penno said.
In March, Synlait reported a 76 per cent slump in earnings to $6.4m for the six months to January.
The company expects to "broadly breakeven" in the full 2021 year.
Synlait shares last traded at $3.11, having dropped by 55.7 per cent over the last 12 months.
Much of Synlait's problems stem from its biggest customer and near 20 per cent shareholder, a2 Milk, which this week revised down its earnings forecasts for the fourth time, and announced the departure of long-serving executive Peter Nathan.
A2 Milk's shares have slumped due to its weakened earnings performance.
They last traded at $5.96 down from their peak last August of $21.50.
The dual-listed a2 Milk company now expects an earnings before interest, depreciation and amortisation (EBITDA) to sales margin for 2021 in the order of 11 per cent to 12 per cent. The guidance in February was for EBITDA margins of 24 to 26 per cent.
Under the forecast, a2 Milk's ebitda would come in at between $132 and $150m, down from $549.7m in the 2020 year.