UK dairy firm Robert Wiseman Dairies has shrugged off rising costs with a set of robust half-year results.

The company, which supplies milk to the likes of Tesco and Sainsbury's, booked underlying operating profit of GBP19.3m (US$39.8m) for the six months to the end of September, up 15.4% on the year.

The rise in earnings came despite Robert Wiseman Dairies seeing costs climb by almost 10%. The milk price the company pays to farmers leapt by 37% since February.

Chief executive Robert Wiseman said better efficiency had helped the company offset costs, while it had also been able to pass on costs to its customers.

"The slow but steady recovery in margins enjoyed over the last few years is due to the improved efficiencies within our supply chain," Wiseman said. "This has undoubtedly been assisted by the stability in contracts with our multiple retailer customers."

Turnover rose 12.2% to GBP327.6m; sales volumes were up 5.2% to 745.6m litres.

Robert Wiseman said its Bridgwater dairy remains "on target" to begin production prior to Christmas.