The 28-year-old prop signed an agreement to join the Vicarage Road club back in January, but has now changed his mind and reopened contract negotiations with the Saints.
But Saracens chief executive Edward Griffiths has hit out at the actions of Northampton and insists the reportedly £1.2m five-year deal has been done.
“Either we operate a game where contracts are respected, or we dont,” Griffiths said. “It’s as simple as that.
“After long consideration, Soane reached a decision that he wished to join Saracens and he duly signed on the dotted line. He subsequently confirmed this decision in press and television interviews.
“Northampton are clearly disappointed by the reality of losing a top player, but their subsequent actions have demeaned the integrity of the game. If every club was to behave as Northampton have behaved in this matter, we would have chaos.”
Saints director of rugby Jim Mallinder said: “He’s told them he doesn’t want to join them. He’s not signed a contract. He’s been back to us and said he’d like to stay. We’re happy to chat about next season.”
l Meanwhile, fly-half Jimmy Gopperth kicked 20 points as Newcastle moved further away from the Premiership relegation zone with a 25-13 victory over Gloucester.
Tom Biggs scored a first-half try for the Falcons, while Tim Taylor touched down for Gloucester.