Tom Beahon, who set up the British sportswear business with brother Phil, fielded questions regarding any involvement with the businessman.
Castore confirmed it had struck a deal with Newcastle United, owned by Ashley, earlier this month.
The Magpies will be the company’s flagship English side having also done a deal with Wolves.
Rangers partnered with Castore for a long-term deal last year following cutting any ties with Ashley and his Sports Direct business which had brought about legal battles.
Any concerns about Castore’s relationship were put to bed by Beahon.
“Ashley is not a shareholder in Castore. The Reuben Brothers aren’t investors. The answer is definitively no.
"We’ve partnered with Rangers and Newcastle because of the opportunity, the potential upside, and it’s nothing to do with Ashley.”