BERLIN (AFP) - Formula One commercial boss Bernie Ecclestone said on Thursday he would diminish his role in the group's operations pending the outcome of a bribery trial set to start in April.

The mop-topped 83-year-old motor-racing magnate was charged last July in relation to a US$44 million (S$56 million) payment he made to former German banker Gerhard Gribkowsky, which was linked to the sale of the Formula One championship rights in 2006.

"According to current plans, the trial is set to start at the end of April," the regional court in the southern German city of Munich said in a statement.

The diminutive tycoon, who turned Formula One racing into one of the world's most profitable sports events, has repeatedly denied he did anything wrong.

But the German court's decision to proceed to trial will create deep uncertainty about his future in the sport.

As a first consequence, Formula One said Ecclestone would step down as head of its holding company pending the outcome of the German trial, although he intends to continue to run the sport on "a day-to-day basis".

"After discussion with the board, Mr Ecclestone has proposed and the board has agreed that until the case has been concluded, he will step down as a director with immediate effect, thereby relinquishing his board duties and responsibilities until the case has been resolved," the holding company, Delta Topco Limited, said in a statement.

"The board believes that it is in the best interests of both the F1 business and the sport that Mr Ecclestone should continue to run the business on a day-to-day basis, but subject to increased monitoring and control by the board. Mr Ecclestone has agreed to these arrangements."

Ecclestone has been under investigation on suspicion of bribery and incitement of fraud since Gribkowsky was convicted of taking an illegal payment when the Formula One rights were sold in a 2006 deal.

The case revolves around rights held by the German bank BayernLB and sold to Britain's CVC Capital Partners for US$830 million.

Ecclestone received a US$66 million commission from Gribkowsky as part of the deal.

Then the Formula One boss allegedly gave him US$44 million of the sum back in exchange for Gribkowsky ensuring that the buyer of his choosing, CVC, would get the rights.

In so doing, prosecutors say, Ecclestone could maintain more control over Formula One business.

'PROVING MY INNOCENCE'

Last June, Gribkowsky was sentenced to eight and a half years in jail in Munich. Ecclestone has always denied bribing the German, claiming he was blackmailed by Gribkowsky.

Having appeared at Gribkowsky's trial, Ecclestone told the Munich state court he felt pressured into paying the cash because he was worried the banker would make unfounded allegations about his tax affairs to Her Majesty's Revenue & Customs.

"I paid because he threatened to go to the Inland Revenue," the diminutive tycoon said at the time.

Ecclestone has put a brave face on the proceedings.

"This is about me proving my innocence," Ecclestone told Thursday's edition of German business paper Handelsblatt.

"That is why I will go to Munich for this trial."

When asked whether he could stay in the driver's seat at Formula One while facing court, Ecclestone said: "In Britain there is the presumption of innocence, you are not guilty until such a verdict has been reached."

His defence team said that statements implicating Ecclestone made by Gribkowsky during his trial were "inaccurate and do not present a coherent story given the facts".

"The claimed bribery never happened," lawyers Sven Thomas and Norbert Scharf said in a statement.

Having been at the top of Formula One for four decades, Ecclestone could face a jail term if convicted by the same court that tried Gribkowsky.

He is also enmeshed in a civil case in London, accused of striking a "corrupt bargain" in a bid to maintain his grip on the sport.

A German media group, Constantin Medien, which claims it lost out in a deal to sell the Formula One group, launched legal action against Ecclestone and three other defendants.

Constantin is seeking more than US$100 million in damages. Media reports said a verdict in the case is expected in the coming days.

And Swiss prosecutors announced in October they were opening their own probe into the issue, in the latest challenge to Ecclestone's authority in a sport he had helped turn into a billion-dollar business.

Striking a defiant note in the Handelsblatt interview, Ecclestone said he had made an offer to buy Germany's fabled Nuerburgring race track, which went on sale last May.

He said he expected an answer in the coming weeks, without revealing how much he would be willing to pay.