After claims from a female employee over 'inappropriate behaviour', ones which Horner still firmly denies, an internal investigation was carried out at Red Bull which cleared Horner of any wrongdoing.
However the saga which has been running since before pre-season testing shows no sign of slowing down heading into next weekend's Australian Grand Prix.
FIA dragged back into Red Bull row
According to the BBC, the woman at the centre of the affair has now registered a complaint with F1's governing body, the FIA, through their ethics committee.
The report adds that there have been two other other reports made to the FIA in the last few weeks surrounding the affair going back as far as early February.
GPFans have contacted both Red Bull and the FIA for comment, but the BBC claim a Red Bull Racing spokesperson was not aware of the complaint and did not want to comment further.
The latest development in the case comes after the employee had already filed an appeal against the ruling that cleared Horner.
It has since been revealed that the female has been suspended from her job at the company on full pay while the saga continues to play out.
While it has not harmed Red Bull on track, following back-to-back wins in Bahrain and Saudi Arabia, it has led to huge splits in the camp, with the likes of Max Verstappen now hinting he could leave the team if the situation is not resolved to satisfaction.