Red Bull have lodged an official protest over Mercedes' dual-axis steering system (DAS) ahead of the season-opening Austrian Grand Prix.
The DAS device allows drivers to move the steering wheel forwards and backwards to adjust the toe angle of the car, leading to both an increase in speed at times and also a reduction in tyre damage.
Mercedes debuted the system on their cars during pre-season testing and both Lewis Hamilton and Valtteri Bottas were seen using it during Friday's practice at the Red Bull Ring.
Reigning world champion Hamilton set the pace in both sessions, finishing ahead of his team-mate as teams prepare for the first race of a 2020 campaign badly disrupted by the coronavirus pandemic.
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In launching a protest to FIA officials, Red Bull have alleged a breach of articles 3.8 and 10.2.3 in the Formula One technical regulations during practice two.
Article 3.8 involves "any specific part of the car influencing its aerodynamic performance must comply with the rules relating to bodywork". Article 10.2.3, meanwhile, relates to the car's suspension system while moving, with no adjustment allowed.
"Obviously we're keen just to get clarity on that system using the mechanisms that are available and getting it addressed quickly early in the weekend," Red Bull boss Christian Horner told Sky Sports prior to the official complaint being made.
"We have a difference of opinion on the system. Its primary performance isn't to steer car obviously so, yes, of course there is a technical position that Mercedes will think one thing, our engineers think something else so in situations like this the best thing is to address it via a protest."
The use of DAS has already been banned for the 2021 F1 season.