The pop star launched his Farrell collection, named after his grandfather, in 2011, and wore items from the range onstage at concerts.
But the company has ceased trading.
Williams says, "I have been fortunate to have had the opportunity to work with the talented Ben DICkens and will miss creating and working with him and wish him every luck for the future."
The news comes at a new low for Williams - earlier this month (Oct13), he confessed he was "gutted" after BBC Radio 1 bosses dropped his songs from their playlist.
The Angels singer was once a staple on the network.