The Van Amersfoort Racing driver took his first series podium on Saturday, but was reported to the stewards after the technical delegate discovered his skid plank was too thin.
Technical regulations require the thickness to be 5mm +/-1mm, while Hughes’ was 3.6mm.
He was subsequently disqualified, promoting Felipe Drugovich to third place for MP Motorsport.
In their report, the FIA said: “The Stewards received a report from the Technical Delegate regarding the nonconformance of Car 24 to the FIA Formula 2 Technical Regulations.
“Car 24’s skid plank was found to have a maximum thickness of 3.6mm, where the Technical Regulations require the thickness to be 5mm +/-1mm. They summoned and heard the team representatives.
“The Stewards heard from the Team representatives who explained that wear on the plank was on the loaded side of the car, and this was likely to be due to variations in tyre pressures during the multiple safety car deployments that occurred.
“Having considered the matter extensively, the Stewards determined that Car 24 did not comply with the Technical Regulations and is therefore disqualified from the results of the Sprint Race.
“The Stewards understand the circumstances that the team explained, and view the matter a resulting from an unfortunate error on the part of the Team and not due to intent.”
Virtuosi Racing’s Jack Doohan received a three-place penalty for Sunday’s feature race and a penalty point after colliding with Logan Sargeant (Carlin) on the first safety car restart.
The stewards said that Doohan “almost unavoidably” ran into the back of Sargeant, but said he was “judged predominantly to blame for the collision.“
The stewards said: “Having considered the matter extensively, the Stewards determined that as the field came through Turn 27 and exited onto the main straight, the rear of the field suddenly bunched up as drivers who had accelerated anticipating a start found the leader maintaining speed and were forced to slow down.
“Car 6 pulled to the left to avoid the cars in front. Car 3 did the same, but there were no open gaps at that point and he almost unavoidably ran into the back of the Car 6. Car 3 is judged predominantly to blame for the collision.
“The blind nature of the exit of Turn 27, which only allowed drivers to see 2 or 3 cars ahead complicated their task during the restart.
“The penalty point assigned is reduced from the those normally assigned due to the difficult position the driver of Car 3 found himself in.”
Prema Racing lodged a protest over the race result after a bizarre incident involving the first safety car.
As the safety car period commenced, the drivers were instructed to head through the pitlane, but the call was immediately reversed with a second message from race control.
But race leader Dennis Hauger - who had started on pole - had already followed the first instruction and fell down the field.
His misery was compounded when the Norwegian was handed a 10-second stop-and-go penalty, which was faced with confusion from the team.
The team is awaiting an outcome of its protest.
