Michael Schumacher's former manager has said that he thinks the family of the Formula 1 legend should come clean with his millions of fans.

Almost four years after the seven-time world champion's skiing crash, almost nothing is known about the extent of the now 48-year-old's brain injuries.

Concurrently, there are unconfirmed rumours that Schumacher will be moved from Switzerland to the US, that his health condition is improving, and that he has relapsed into coma.

Willi Weber, who was Schumacher's long-term manager, blames the confusion on the great German's family and current management.

"I find it very unfortunate that Michael's fans do not know about his health. Why are they not being told the truth?" he asked.

Weber was speaking to the Munich-based newspaper TZ, shortly after an operation on his back.

"Formula 1 is just like my back now - painful," he said.

"It is now a Mickey Mouse show and nothing else. The sport has gone into the background."

The 2017 calendar continues with the United States Grand Prix on Sunday.