Triple world champion Lewis Hamilton says the new 'halo' head protection device is "too drastic" and wants to be able to choose whether to use it.
The Mercedes driver, 31, has already described it as the "worst-looking" modification in Formula 1 history.
"I understand safety is a huge issue and something we have to work towards, but this is not the one," he said.
Ferrari's Sebastian Vettel said the device can be as "ugly as possible" as long as it helps save lives.
The German, a four-time world champion, said Henry Surtees and Justin Wilson would "still be around if we had this type of system".
Surtees and Wilson were both killed when hit by debris while racing in other forms of motorsport.
"Nothing justifies not having these guys around anymore," said Vettel.
Hamilton said F1 cars had lost "the cool look they used to have in the 1980s and 1990s", adding: "It is not F1 for me.
"If they do implement it, I hope we have a choice of whether we have to use it and are not forced to, because ultimately it is our safety."
What is the 'halo'?
It is a structure that fits over the cockpit to protect the driver from flying debris, but retains an F1 car's open feel.
A prototype version has been tested by Ferrari at this week's final pre-season test in Barcelona, with a view to it being rolled out to all cars in time for 2017.
Why is it being introduced?
To protect drivers from large pieces of flying debris following a series of deaths and injuries across motorsport.
It has the support of the Grand Prix Drivers' Association, of which the vast majority of drivers are members.
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Who came up with it?
The design was agreed by all the teams and sport's governing body, the FIA, after years of research.
However, it is not necessarily the definitive design that will be used next year as further testing still needs to be done on the strength of the mounting points.
Has there been much reaction?
You've read what Hamilton and Vettel think, but other drivers have had their say, too.
It's fair to say that the 'halo' has split opinion, with some drivers all for it and others against because it 'sterilises' the sport.
Does it work?
Vettel thinks it will, but it remains to be seen. Some observers have questioned whether it could restrict visibility.
Former world champion Kimi Raikkonen, who did two laps with it on Thursday, said his view was "a bit limited in the front" but said the design could still be tweaked.
Ferrari team-mate Vettel said "you can see what you need to see", adding: "I tested it in the simulator and I think we will see evolutions of it very soon."
So who is against it?
Hamilton, obviously, but Force India driver Nico Hulkenberg is not a fan either.
The German insists F1 needs to retain an element of danger to remain "sexy and attractive".
And who is for it?
Two-time world champion Fernando Alonso says it is a "step in the right direction" because "head protection is the weakest link in safety".
Hamilton's team-mate Nico Rosberg thinks the device is "quite cool" to look at and a "really massive step in safety".
Red Bull's Daniel Ricciardo commented: "The cars from 2008 to 2009 had a big change [visually], the cars were ugly. The halo isn't as dramatic as that."
"I heard Hulkenberg say some things I don't agree with, because there's no need to be a hero about the situation.
"It doesn't change the sport, or the speed of the car - it's just if there are any flying objects, it's an extra bit of protection for us.
"I don't know why he's puffing his chest out for something like that, it doesn't make sense."
What other options are there?
Red Bull are proposing a different solution, which one source described as a "half canopy".
Team boss Christian Horner says they plan to run it on a show car next month, but one senior insider told BBC Sport that the design "doesn't look very promising".
What happens now?
F1 bosses are pressing ahead with plans to introduce the 'halo' in 2017.
It still needs some fine-tuning - and the mounting points to the chassis have not been subject to comprehensive load-testing yet - but it seems inevitable that F1 cars will feature a design similar to that seen on the Ferrari this week.