A video said to show the panicked final seconds inside the cabin of Germanwings flight 4U925 before it crashed into a mountainside in the French Alps is authentic, the French magazine Paris Match has insisted.

Questions have been raised about the veracity of the video after a senior French police spokesman said the magazine’s story was false and the French state prosecutor said no video footage had yet featured in the inquiry evidence. The spokesman added that if any film were to exist it should immediately be handed to investigators.

Paris Match stood by its story, written in collaboration with the German newspaper Bild. Neither publication broadcast the footage but instead described the “totally blurred and chaotic” scenes.

They claimed the film showed how the passengers were aware of their fate in the last moments of the Barcelona to Düsseldorf flight, which crashed into the mountainside at 435mph (700kmh) last Tuesday, killing all 150 people on board. Prosecutors in France and Germany have suggested that the co-pilot, Andreas Lubitz, deliberately crashed the plane.

In a video interview on the Paris Match website, Frédéric Helbert, the senior investigative reporter who wrote the story, said he and the editorial team had watched the “chilling” and “moving” film dozens of times. He said it had been shot by someone at the back of the plane and did not identify passengers, who were all seated.