Robert Wiseman Dairies has warned that its profits will be hit by rising energy costs and a slump in the value of bulk cream.

Operating profits for this financial year could be affected by as much as £8.5m as a result of the "significant pressures" from rising cost increases in oil and plastics, the processor said.

The warning came as the company posted profits of £38.4m for the financial year to 29 March 2008, up 10.1% on the previous year.

Sales volumes also increased by 4.1% to a record 1.52bn litres, the company said.

Alan Wiseman, company chairman, said the results were "satisfactory".

"However in recent months we have faced an accumulation of cost and revenue pressures that will, disappointingly, impact our profitability in the current year.

"Despite short-term margin pressures, we are confident that the business is in good shape," he said.

"We strongly believe this will provide us with the platform to continue our successful growth in the period ahead."

The dairy has also announced it has increased its milk price by 0.5p/l to 26.2p/l from 1 May.

The increase means the company has increased its milk price to members by 40% since February last year.