Hammers manager Sam Allardyce revealed today that the club have missed out on signing the 31-year-old, who was offered a short-term deal until the end of the season with an option for a further year.
Despite receiving a lifeline from Upton Park, it is understood that Warnock has decided to move to Elland Road, according to Sky Sports News.
"Stephen we thought was a go-er but another club in the Championship made him a more long-term offer which I think he has accepted, so I think he has decided to take that so that," Allardyce said in a press conference. "A lot of hard work that went to waste again."
Warnock, who spent a period on loan at Bolton Wanderers, has not featured for Villa this season.