Former Formula One boss Bernie Ecclestone has given a rare glimpse into the condition of stricken icon Michael Schumacher - but it's not the news fans have been waiting for.

Schumacher, a seven-time world champion, suffered severe head trauma in a skiing accident in the French Alps in December 2013 and was placed in a medically induced coma shortly after.

His condition has been a closely guarded secret, with only sporadic updates from his family.

In a trailer for a new documentary on the F1 legend's life, Ecclestone, who stepped down as F1 chief executive in January 2017, has given a unique insight into Schumacher's health.

"He is not with us at this moment. But when he is better, he will answer all the questions," Ecclestone says in the trailer for Schumacher.

According to the Mirror, the trailer for Schumacher was shared with German media this week. The film is set to be released on December 5.

The trailer reportedly also features snippets from interviews with Schumacher's wife Corinna.

According to the Mirror, Corinna says she is hopeful her husband will make a full recovery, telling the interviewer: "Michael is a fighter and will not give up".

Michael Schumacher, his wife Corinna, and Bernie Ecclestone in 1995. Photo / Getty

Schumacher's 73-year-old father Rolf is also expected to make an appearance in the documentary, which filmmakers Michael Wech and Hanns-Bruno Kammertöns say will even feature never-before-seen archive footage belonging to the family.

Producers of the film say it was made to mark Schumacher's 50th birthday, which was in January and the 25th anniversary of his first world title win.

"It will show him as a remorseless and daring Formula 1 driver, the ambitious sportsman, the accomplished mechanic with a unique technical flair, the reliable team player and the loving family man," they said.

Benjamin Seikel from B14 Film hailed the family's trust with such a sensitive and ambitious film.

"We're very happy about the trust that Michael Schumacher's family and management have shown us. Without their support, this film would not have been possible," he said.

"It's time for this film. But of course we're very aware of the responsibility that comes with it."

Schumacher, who retired from racing in 2012, is being cared for at home in Switzerland.

Earlier this year he was reportedly spotted arriving at his family's holiday home in Majorca.

German magazine Bunte reported that Schumacher spent the holidays, including his birthday on January 3, at a luxury villa on the Mediterranean island before returning to his home at Lake Geneva.

Schumacher's spokesperson, Sabine Kehm, last year rejected reports the seven-time world champion would be moved to Majorca permanently as he continues his long recovery.