Mercedes are at the center of a row over the legality of their car after introducing a radical new design at the second pre-season test.
Ross Brawn, the managing director of Formula 1 said the car's sidepods were very extreme interpretations of the regulations.
Red Bull team boss Christian Horner told Germany's Auto Motor und Sport that Mercedes have gone a step too far.
He said that that does not correspond to the spirit of the regulations.
These wings are illegal for us.
Red Bull initially described the quotes as "incorrect", before clarifying they were not official.
I was surprised to read comments that I was supposed to have made.
I haven't paid much attention to the Mercedes car. It is a fairly different concept, but that is for the designers and the aero guys to get into.
The revised Mercedes has been dubbed the "no sidepod car" because of the extreme way the world champion have shrunk the bodywork next to the driver.
The integration of a shaped side-impact structure on which the rear-view mirrors are mounted seems to have been taken issue by Horner.
Those are not mirror mounts, but two wings. They have built vertical baffles. The mirror mount has nothing to do with them.
Binotto raised questions about the Mercedes design.
He said that it was a great car and that it was different to ours.
We were not expecting that on the mirrors. The mirror should not have an aerodynamic purpose and the way they treated their cars there is a significant aerodynamic purpose in the mirrors.
The risk in the future is that all teams will start designing mirrors that look like spaceships. It is something we need to discuss in the spirit of what we intend to do for the future.
Wolff said he wasn't concerned about any problems with the rules.
Wolff said the governing body was involved in the design process.
Wolff said it was clear that when you come with an innovation it creates a debate.
We wanted to be in touch with the FIA and not run alone. I think it will be okay.
If eight of the 10 teams agree, rules can be changed mid-season.
He said that once the interpretation Mercedes has made has been understood, we can get a balanced view on what impact it will have.
Thespirit of the rules is a grey area. The wording of the regulations can be changed with an 80% team majority.
The teams are aware that something can happen if something slips by in the rule-writing process. During the season that could happen. We will have to see how this one plays out.
Brawn said his main concern was whether the designs of teams undermine the intent of the rules to make racing better by allowing cars to follow each other more closely than in the past.
Pierre Gasly of Alpha Tauri set the fastest time of the day, ahead of the cars of Charles Leclerc and Carlos Sainz and Lance Stroll.
Headline lap times in testing are unreliable because teams can alter their cars specification to affect lap time.
After Russell drove in the afternoon session, he was ninth and 11th fastest, while Hamilton went out in the morning.
Russell said that the new features of the car are not about how it looks, but how fast it goes. It caught a lot of people's attention this morning.
I am proud to be part of a team that is pushing innovation and seeing something pretty spectacular being pulled off is pretty incredible.
The session was stopped eight minutes early when Red Bull's Sergio Perez had a spin and accidentally reversed into the gravel and became stuck when trying to get going again.
1 Pierre Gasly (Fra) Alpha Tauri.
Carlos Sainz (Spa) is a driver.
Charles Leclerc is from Monaco.
4 Lance Stroll (Can)
5 Alex Albon (Tha) Williams
Lando Norris (GB) is a McLaren driver.
7 Valtteri Bottas is a driver.
8 Sebastian Vettel (Ger)
George Russell is in a Mercedes.
10Sergio Perez (Mex) is a Red Bull athlete.
Lewis Hamilton is with Mercedes.
Fernando Alonso is in the Alpine.
13 Esteban Ocon is in the Alpine.
Alfa Romeo 1:37.164 is the home of Zhou Guanyu.
Pietro Fittipaldi is fromBra
The C4 and C2 are the same tire. C1 is the hardest.