Sporting Lisbon director Nuno Saraiva has published a strongly-worded statement attacking David Sullivan and calling the West Ham co-chairman a lying parasite.
Gold told West Ham's official website earlier this week that he had made a club-record bid for Sporting midfielder William Carvalho, but Saraiva has denied this.
Saraiva has suggested that Gold lied about trying to sign Carvalho in order to impress West Ham supporters with his supposed ambition. But Gold's claims have damaged Sporting's reputation, Saraiva said.
Saraiva questioned the integrity of Gold, who owns Ann Summers and used to run an adult magazine company.