The company which supplies growing media, fertilisers and chemicals to Wyevale Garden Centres, B&Q, Tesco, Wilkinson, and Morrisons, as well as independent garden centres and garden centre groups, has recorded a loss of £3.5m in the six months to 31 March.
The loss in the equivalent period in 2014 was £1.8m.
Revenue was £18.7m, down from £21.8m in the equivalent period in 2014.
Exceptional costs of £2.4m (2014: £1.3m loss) and an exceptional impairment charge on properties of £2.2m were also recorded.
Sinclair said its Ellesmere Port supersite was now operational, that investment in J Arthur Bowers ranges had "improved sell-through", retail quality had improved, the management team had been reinforced and Knottingley and Oswaldtwistle sites had been sold.
Chief executive Stuart Burgin said: "Since I joined William Sinclair as CEO on 5th March there has been a huge level of activity in the business. This has been focused in two key areas: improving the performance of the Ellesmere Port site, and analysing the business and developing plans for the future.
"I am pleased to say that commissioning of Ellesmere Port has moved forward considerably and that we have developed strong plans for the future revolving around a single point of dispatch from Ellesmere Port and increased focus on customer and product profitability.
"Provided we are successful in raising the funds required to implement these plans, I am confident that William Sinclair can be successful again."