Jules Bianchi's father Philippe feels Formula One bosses "must go further" with cockpit safety after being left unconvinced by the new Halo device.
Kimi Raikkonen became the first F1 driver to run with the Halo closed cockpit system during Thursday morning's testing in Spain.
The Halo is designed to shield drivers from flying debris and prevent the sort of accident which killed Henry Surtees in 2009. Surtees, the son of 1964 world champion John, was killed after he was hit on the crash helmet by an errant tyre while competing in a Formula Two race at Brands Hatch.
F1 driver Bianchi also succumbed to the devastating injuries he sustained at the Japanese Grand Prix in July, although it is not believed improved head protection would have saved the Frenchman.
Bianchi's father says the Halo device does not provide a total fix for the dangers of an open cockpit and called on the F1's governing body, the FIA, to do more when it comes to driver-safety.
"I consider that this is a step forward in terms of security," Bianchi told French television channel Canal+. "It is obvious that in the case of when a wheel comes off, this system would be effective.
"However, in the case of small debris, as Felipe Massa and Justin Wilson (the Indycar star who was killed last August) had, that wouldn't have changed anything. So this is a step forward, but it does not solve everything."
Bianchi says such a concept would not have helped his son in his accident at Suzuka in October 2014.
"For Jules, it would not have changed nothing, because it's the extremely violent deceleration that caused the damage that we know to his brain," Bianchi said. "I think developments of the HANS system to better absorb big deceleration in a severe impact could help in this case.
"This is obviously not me who would raise myself against something that brings more security to drivers, but the version of this Halo system did not convince me and has yet to be perfected.
"Aesthetically, it's pretty bad, and I wonder what the driver gets to see behind the Halo. The FIA wished to act after Jules's and Justin's accidents, but it must go further."
The governing body has explored a number of designs aimed at protecting drivers from flying debris after Massa was struck by a spring from Rubens Barrichello's Brawn during qualifying for the 2009 Hungarian Grand Prix. F1 race director Charlie Whiting told teams earlier this year that the FIA is making sure the Halo -- a concept originally developed by Mercedes -- was in place for next season.