Family-owned spice products group Watkins Inc. has filed a lawsuit alleging that spice maker McCormick & Co. underfills tins of its ground black pepper in a manner that "misleads retailers and consumers".

The complaint alleges that McCormick, the largest distributor of tinned black pepper in the US, has sold ground pepper in "non-transparent metal tins" for "decades". However, in early 2015 the company began selling the same sized tins with 25% less pepper, Watkins asserted.

The court documents claim that this constitutes "slack filling" which is illegal under state and federal law.

McCormick was unavailable for comment at time of press.