Adrian Newey, Red Bull's technical director and the most respected designer in Formula One, is worried about the safety of the new low nose which is the most conspicuous feature of this year's radical technological changes.

On the first morning of the opening testing session in southern Spain, which was remarkably quiet as teams came to terms with their complex new engines, Newey said: "The regulation has been introduced following some research by the FIA [the sport's governing body] which suggests that nose height reduces the chance of cars being launched [into the air] like the accident that Mark Webber had when he hit the back of Heikki Kovalainen in Valencia a few years ago. I must admit, I am concerned that the opposite may now happen, that cars now submarine effectively.

"If you hit the back of a car square on then you go underneath and you end up with a rear crash structure in your face, which is a much worse scenario."

Most of the cars introduced in recent days have had low, sloping noses, making them look a little like anteaters, though those unveiled by Mercedes and Red Bull on Tuesday morning were less ugly than most.

Newey added: "There have been some accidents where you think would a low nose possibly have made things much worse? There was the accident a few years ago where Michael Schumacher span at the first corner and somebody mounted him. Would a low nose have made that worse?

"I guess it's like all these things, it might help in some scenarios, it hurts in others. It's one which I must admit, personally I'm not in favour of. For me it's introduced possibly more dangers than it has cured."

Red Bull's team principal Christian Horner, when asked to comment on Newey's observations, added: "Adrian has never been a fan of this nose concept of torpedoing a car underneath another rather than going over the top.

"But that's the duty of the FIA and they're responsible for the safety in the sport. They've done their research and come up with the regulations. I don't think their regulations intended to have noses that we've seen, that aren't beauties, but their priority is for safety. Inevitably there will be concerns and differences of opinions."

The team's four-times world champion, Sebastian Vettel, added: "First of all, there is always a risk when you step into the car and you cannot manage what you do, unless you don't run.

"The nose rule was introduced to stop cars from lifting off behind another car. Hopefully we will not have a situation like that. For some things they might be safe for others, maybe not …"

The 2014 cars come with a whole raft of changes, the most important of which is the power unit, in which the old V8 has been dropped in favour of a new 1.6litre turbo-charged V6. But, in turn, this has resulted in new aero regulations.

Jerez was a very quiet place on Tuesday as even engineers and mechanics were left scratching their heads as they completed system tests to make sure the cars were ready for the track. The four-day testing session will end on Friday and will be completed by two further tests in Bahrain next month.

Red Bull is "slaving around the clock" to solve its problems ahead of next weekend's season-opening Australian grand prix.

It is emerging that, amid the reigning world champions' obvious problems with engine partner Renault and the new turbo V6 'power unit', the actual basic design of the Adrian Newey-penned RB10 is sound.

Lewis Hamilton calls the car "stunning", and McLaren's Jenson Button thinks it is also fast.

"I was with (Daniel) Ricciardo for several laps and he couldn't pass me on the straights," said the Briton at the end of pre-season testing in Bahrain.

"He passed me on the outside of turn 11, which is high speed -- I've never seen anything like that before," Button is quoted by Spain's Marca sports newspaper.

Red Bull's Dr Helmut Marko said the team's normal development processes are also working well ahead of the new season.

"Our measurements have shown that the new parts we were bringing worked as desired, making the car better," he is quoted by Germany's Auto Bild.

"The fact that it did not look good on the track was due to the engine software," he revealed.

Marko said Red Bull and Renault are working hard together in the remaining days until Melbourne.

"We have so much to do," he told Bild newspaper, "especially the guys responsible for the software who will now slave around the clock on 18 hour shifts.

"But whoever can win together, can also work hard together," Marko added.

Mercedes is the clear early-season title favourite, but the German squad's Toto Wolff is not writing off Red Bull.

"I am sure they will come back," he is quoted by the Frankfurter Allgemeine Zeitung newspaper. "The only question is when.

"In our view, hopefully as late as possible," Wolff is also quoted by APA news agency.

Those on the outside, however, are less sure Red Bull can recover quickly.

"I think a Mercedes will win the title," former F1 driver Timo Glock told T-online.

F1 chief executive Bernie Ecclestone is not unhappy his friend Sebastian Vettel and Red Bull are struggling, telling Bild newspaper the fans need a new winner to make the sport "exciting" again.

He added: "Red Bull are not going to run away just because they don't win everything again."