Red Bull Formula 1 boss Christian Horner says he has a "sour taste" with Ferrari’s continued performance slump showing it was hit hard by its controversial engine settlement with the FIA.

A number of power unit-related clarifications issued over the winter have reined in Ferrari’s previous straightline advantage that it enjoyed for much of the 2019 season and left the Italian squad battling in the midfield.

Ferrari has openly admitted that the private settlement it reached with the FIA after pre-season testing in February has resulted in a significant loss in competitiveness.

A Ferrari Horror Show | F1 Winners & Losers Belgian GP |

Horner says the situation has “left quite a sour taste” and believes that Red Bull could have won the races which Ferrari triumphed in last year.

“The whole thing has left quite a sour taste,” Horner replied when asked if the situation was frustrating.

“I mean obviously you can draw your own conclusions from Ferrari's current performance but, yeah, there are races that we should have won last year arguably if they had run with an engine that seems to be quite different to what performance that they had last year.”

Ferrari’s struggles continued throughout the Belgian Grand Prix weekend as Sebastian Vettel could only finish 13th, ahead of teammate Charles Leclerc. Both drivers were beaten by the Ferrari-powered Alfa Romeo of Kimi Raikkonen.

It marked a huge contrast from last year’s race at Spa, which Ferrari dominated as Leclerc claimed his maiden F1 victory.

“It's obviously very tough for them but I think their focus has obviously been in the wrong areas in previous years, which is why they're obviously seem to be struggling a little with whatever was in that agreement,” Horner added.

“I think you've got Mercedes as a clear leader, then I think Honda and Renault are reasonably close depending on circuits and conditions. And then you've got Ferrari obviously at the back of the queue.”