"The affected product should not be used as counterfeit medicines are not subject to the rigorous safety and quality checks by GSK, as is the case for genuine Grand-Pa powders," the company said in a statement on Thursday.

The counterfeit products are being sold as Grand-Pa Powders, 38-count, and have batch numbers 309339 and 314020.

The counterfeit powder is being sold in packaging that has subtle differences from the genuine product. The fakes have spelling errors in the text on the package. For example, the word "koors" is misspelled "kors".

The company said it was testing the counterfeit powder at its laboratories in the United Kingdom to establish the contents of the fake product.

GSK said it was voluntarily recalling its own products bearing those batch numbers in an effort to protect consumers.

It asks that consumer call its help line, 0800-118274, if they have queries or need assistance.