This latest lawsuit, filed in December, hinges on "deceptive and/or misleading representations", made by the sweetener firm in "advertisements and marketing terminology" to consumers, says the association.
Merisant, the US maker of tabletop sweetener Equal and NutraSweet and a competitor to Splenda, alleged in November that the product's marketing slogan, "made from sugar, so it tastes like sugar," had mislead consumers into thinking the artificial sweetener was "natural."
But McNeil Nutritionals asserts that sucralose starts off as pure cane sugar, and is then chemically altered in the manufacturing process to create a new compound with zero calories and 600 times sweeter than sugar.
A currently booming market for the Splenda product may, or may not, feel the impact of the US court cases.
"From our perspective, whatever the outcome of the litigation, sucralose will still be made from sugar, and still taste like sugar," a spokesperson at Tate and Lyle, that manufactures the Splenda brand, told FoodNavigator.com in December.
Sucralose was developed jointly by McNeil Nutritionals and sugar giant Tate & Lyle. The British firm became the sole manufacturer of Splenda earlier this year after reaching an agreement with McNeil Nutritionals.
More than 3,500 products are now sweetened with sucralose, the companies claim. The ingredient retains its taste after being heated, which means it is suitable for use in products that are baked and pasteurised.
According to Datamonitor, the ingredient was used in 1,436 new products worldwide in 2004, up from 573 in 2003 and 35 in 1999.
Growth looks strong on the back of rising health concerns, driving consumers towards sugar free products and food makers introduce zero-calorie or low-calorie sugar substitutes into their new product formulations.
Market analysts Freedonia predict growth of intensity sweeteners at around 8.3 per cent year on year until 2008, with sales rising from a small base of $81m in 1998 to $189m in 2008.
Such is the success of the sugar replacer, used by international players like PepsiCo, General Mills and Unilever, that Tate & Lyle warned at the end of last year it would prioritise needs of existing customers as demand for the additive 'far exceeds our expectations.'
Rationing supplies, the British firm said it would not be taking on any new customers in the US until the Alabama plant extension in 2006 and the new Singapore plant in 2007 come on line.
Sucralose (E955) is permitted in 40 countries, but has only recently been accepted onto the EU25 market through an amendment to the 1994 EU Sweeteners Directive (94/35/EC), cleared in February this year.