Tate & Lyle has been dealt a blow by US patent authorities in its battle over calorie-free sweetener sucralose.

Chinese manufacturers producing generic versions of the sweetener, marketed as Splenda by Tate & Lyle, were found by the US International Trade Commission in a preliminary judgment not to have violated patents held by the UK company.

Shares in the sugar giant dropped by more than 10% following the ruling, which comes with Splenda having lost market share to rivals over the last year. The sweetener accounts for around a fifth of the group’s profits.

“We would not have proceeded with an ITC case unless we believed we had adequate evidence to demonstrate that our patents are being infringed,” Tate & Lyle general counsel Robert Gibber told The Times.

A final ruling is expected early next year.

Last week Tate & Lyle confirmed that its finance director, John Nicholas, is leaving the group at the end of September after just two years in the role.