Renault sporting director Alan Permane has raised a new legality question over Mercedes' DAS system.

The Dual-Axis Steering device was the talk of the paddock during Formula 1 testing last week after it was used for the first time on Thursday.

It works by the driver pulling the steering wheel toward them on the straight to toe-in the front wheels before returning to their normal toe-out position when the steering wheel is pushed back into place before the corner.

Mercedes revealed DAS has been in development for around a year and though many have praised its ingenuity, team boss Toto Wolff was initially a sceptic.

"It’ll never work," the Austrian said was his first reaction to Auto Motor und Sport. “As a driver, you don't want to pull, push and steer at the same time."

But after Mercedes' engineers allowed Wolff himself to test it out, his opinion changed.

“I was surprised at how easy it was," he admitted. "It’s an unnatural movement, but the stroke is short and you're only doing it on the straight.”

After it was first spotted, speculation over its legality was rampant with Red Bull quickly declaring it a breach of suspension regulations.

But because the system is linked to the steering, the FIA disagreed and it will be allowed in 2020, though has already been banned for 2021.

However, Permane has now raised a new point which could lead to protests without clarification.

“We don't know what it is doing. James Allison [Mercedes technical director] and his men have done something clever, and undoubtedly they think there is plenty of lap time in it," he said via Motorsport.

“I'm sure they've been through it with probably Nikolas [Tombazis], the FIA and his guys and are happy it's legal. I agree.

“There's probably a parc ferme question mark over it, but I suspect that the detail lies in is it a steering system or a suspension system? The two in the technical regs are defined differently and that's where the detail is.”

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What the Renault sporting director is referring to is under the regulations, when a car first leaves the garage for qualifying, changes to the car are not permitted but for a small number of exceptions.

Article 34.6 also adds: “A competitor may not modify any part on the car or make changes to the set-up of the suspension whilst the car is being held under parc fermé conditions.

“In the case of a breach of this Article, the relevant driver must start the race from the pit lane and follow the procedures laid out in Article 36.2.

“In order that the scrutineers may be completely satisfied that no alterations have been made to the suspension systems or aerodynamic configuration of the car (with the exception of the front wing) whilst in pre-race parc fermé, it must be clear from physical inspection that changes cannot be made without the use of tools.”

FIA race director Michael Masi wouldn't comment on that point but it does stand to reason that, if it's declared a steering system under the technical regs, a similar stance would be taken on the sporting rules as well.

Still, it's another talking point of many more that are likely as the DAS debate continues.