Tate & Lyle has claimed that three Chinese firms have infringed patents protecting methods used in the production of the UK company's artificial sweetener sucralose.

Tate & Lyle has filed a case with the US International Trade Commission against the three Chinese companies. The company said the US case has also been bought against 18 importers and distributors.

The three Chinese manufacturers named in the case are Hebei Sukerui Science and Technology, Changzhou Niutang Chemical Plant and Guangdong Food Industry Institute.

"Our sucralose manufacturing technology is protected by a robust and sophisticated patent estate, which we will defend rigorously," said Robert Gibber, general counsel of Tate & Lyle, today (10 April).

Tate & Lyle filed a similar case in last year, which, so far, has resulted in a favourable settlement for the company against three of the ten defendants.

Sucralose, which is sold under the Splenda brand name, accounts for about 20% of Tate & Lyle's annual profits.

However, the market for the artificial sweetener is constricting, having been hit by a decline in US fizzy drinks sales. In January, the group issued a profit warning following weaker-than-expected Splenda sales.