Mercedes' innovative F-duct rear-wing design has been declared legal by FIA stewards, ahead of the Chinese Grand Prix, following a protest by Lotus.

The controversial design features holes in the endplate, which helps to cut downforce and increase top speed. But several teams have registered their belief that, because the mechanism is incorporated into the drag reduction system, DRS, it is activated by the driver. Something that would be illegal.

However, Mercedes claim that the device is independent of the DRS, which is driver-activated and helps overtaking when used at specified points on the circuit.

And a four-man panel of FIA stewards has ruled in favor of Mercedes. The design passed inspection at each of the first two grand prixs of the 2012 Formula One Season and had also been cleared in Shanghai ahead of the Chinese Grand Prix, which takes place on Sunday.

Several constructirs vocalized their unhappiness with the design before the Malaysian grand prix last month, leading to Mercedes team chief Ross Brawn to vent his frustrations with the sustained complaints.

Bang a protest in on Thursday if you want to get it done, and leave the stewards to try and resolve the issue, he said, according to the Guardian. Don't do it after qualifying or the race and spoil the event.

I can understand people are frustrated because they haven't thought of the idea, or they don't believe it's correct, and that's their right. But I've seen lots of things on racing cars where I've wondered at the interpretation, but that is the nature of our business.

And Brawn, speaking in Shanghai before the protest was lodged said that the significance of the design had been blown out of all proportion.

Obviously there's benefits in the system, but Lotus were quoting they have a 0.2secs benefit [from new parts] coming here, Brawn said, according to the BBC.

Well, I can promise you our system is definitely not 0.2secs, particularly in the race.

Lotus are not expected to appeal the decision, according to Formula1.com. That means that the rest of the paddock now face a decision on whether to invest in the design, which has seen Mercedes perform strongly in qualifying so far this season, themselves.

A similar situation occurred over the past couple of years when Red Bull pioneered exhaust-blown diffusers, which played a significant role in the team's dominance that led to Sebastian Vettel claiming consecutive driver's titles.

When the benfits of the sytem became obvious teams protested, while simultaneously trying to copy the design, before the blown-diffusers were banned coming into this season.