The Red Bull boss has voiced concerns over the legality of the rear wing on the Mercedes, with allegations the main plane on the W12 flexes.
This was supported by an image issued to the media which appeared to show score marks on the Mercedes end plate.
It forms part of a dossier of evidence Red Bull has been gathering over its world championship rival, which includes images that stretch back to the Hungarian Grand Prix.
Key among the concerns held at Milton Keynes in the additional straight line speed Mercedes has enjoyed in the second half of the season.
A number of possibilities have been raised, including trick rear suspension, a significant power boost from a new internal combustion engine, and flexible rear wings.
On the latter, a technical directive was introduced earlier this season to prevent rear wings leaning backwards underload – a design Red Bull had adopted while Mercedes had not.
“We're not going to disclose our full protest document here, it's just to give you an example of what is happening and why we're seeing this exponential straight line speed,” Horner told Sky Sports.
“So the FIA's got all that, they're the people that can go and check these things.
“And, you know, really delighted to see that they've introduced a fact-finding mission here, that after qualifying, they're going to be testing these wings.”
Horner explained that the post-qualifying test would see additional load added to the rear wing.
“[A] pull down test on the back of the wing,” he responded when asked what the additional test would be.
“So effectively, an amount of load will be added to the back of the wing.
“I think it'd be probably closer to, split across the wing, is probably going to be 70/80 kilos, and it'll be ramped up in stages.
“So you'll see what you'll be able to measure the deflection.
“It's great that the FIA is being proactive, they're looking at it, because our concern isn't so much here, where straight line speed isn't at the premium that it is, potentially Saudi and Abu Dhabi.
“So we're glad that they're taking this very seriously.”
Mercedes boss Toto Wolff has rejected suggestions his team is doing anything untoward.
Asked by Horner during Friday's FIA press conference how he explained the scoring witnessed on the rear wing end plate, he responded: “I think it's within what is allowed and, therefore, that's okay.”
Speedcafe.com has contacted the FIA for confirmation.