Horner says that due to Alfa Romeo's forthcoming involvement with Ferrari their threats to walk out if the new engine regulations do not suit them in 2021 are somewhat disingenuous.
Ferrari boss Sergio Marchionne has threatened to pull the team out but Horner says they would have never brought Alfa Romeo back into the sport if they were really considering doing that.
"They (Alfa) come under the same management as Sergio so I can't believe he'd have brought Alfa Romeo in for Ferrari to be leaving in a couple of years," he told Reuters.
"I think it demonstrates that Formula One is obviously working and creating the recognition, otherwise the group wouldn't have brought the Alfa brand into Formula One."
He added: "Formula One needs Ferrari and Ferrari needs Formula One."
The Alfa Romeo brand is returning to Formula 1 after agreeing a new partnership with the Swiss-based Sauber team, the move strengthens the links between Sauber and Ferrari, which is a sister brand of Fiat-owned Alfa Romeo.