MERCEDES boss Toto Wolff has called for Red Bull’s investigation into Christian Horner to be transparent — and said the controversy is “an issue for all of Formula One.”

Horner is under investigation by the racing team’s parent company Red Bull GmbH following a claim of “inappropriate behaviour” by a female colleague.

The 50-year-old emphatically denies the accusation and remains in his role as Red Bull team principal.

He is in Bahrain for this week’s three-day test ahead of the opening race, also in the Gulf Kingdom, on March 2.

And Horner has stated it is his intention to be in his post for the start of the new campaign.

“It is clear,” Wolff said when asked to address the allegations during the lunch interval on the first day of testing.

“Formula One and the teams stand for inclusion, equality, fairness and diversity, and that is not only about talking about it, but living it day in, day out. These are just standards we set ourselves.

“We are a global sport and one of the most important sport platforms in the world and role models, too.

“But having said that, there is a lot of speculation that has been happening over the past weeks and lots of things that are going on.

“What is important at that stage is for a process with rigour. I think what Red Bull has started as an independent investigation, if this is done in the right way, with transparency, that is something we need to look at.

“What the outcomes are, what it means for Formula One, and how we can learn from that because we want to talk about racing cars and we want to talk about the sport, rather than these very, very critical topics that are more than just a team issue.

“It is phenomenon, and an issue for all of Formula One, and every individual that works out there.”

Horner is due to be in the media spotlight at an F1 press conference alongside four other team principals on Thursday.

Speaking at Red Bull’s car launch last week, Horner said he was unable to provide a timeline as to when the investigation will be completed.

It is understood both Red Bull and Horner are keen for a swift resolution, but sources have indicated that a conclusion is not imminent. F1 bosses have called for the controversy to be “clarified at the earliest opportunity.”

Max Verstappen put Red Bull’s off-track troubles to one side by setting the pace in the opening session on Wednesday.

The three-time world champion ended the running nearly seven-tenths quicker than Ferrari’s Charles Leclerc, with Aston Martin’s Fernando Alonso in third, eight-tenths back, and the only other driver within one second of Verstappen.

George Russell was sixth for Mercedes, 1.68 secs off the pace. Lewis Hamilton gets his first taste of the final Mercedes he will drive on Thursday ahead of his blockbuster switch to Ferrari next year.