Red Bull design guru Adrian Newey admits he was extremely concerned at tyre safety during the Belgian Grand Prix, describing the race as one of the scariest he's been involved in.

The Englishman, who has won titles with Williams, McLaren and Red Bull, was concerned at blistering to the front tyres on both its cars, though Pirelli places the blame entirely at the Austrian outfit's door.

Ahead of the race, Red Bull and a couple of other teams sought permission from the FIA to change the tyres, however, the call was denied since the rules dictate that tyres can only be changed before the race if they are damaged.

In the hours leading up to the race, the Milton Keynes outfit looked at various options including changing the camber of the cars, which would necessitate starting from the pitlane. At one stage TV cameras picked up on Sebastian Vettel having an animated conversation with a Pirelli engineer in the paddock, the German looking far from happy.

Pirelli' motorsport boss, Paul Hembery, though denying a safety issue admitted that there was blistering. However, he put this down in part to the lack of dry running over the course of the weekend and Red Bull's decision to exceed his company's recommendations in terms of camber. While the Italian manufacturer recommends a maximum camber of four degrees. Newey admits that on the Red Bull it was "just a hair over four, four and an eighth, or something, just a tiny bit over".

"Obviously if we had known there was a safety concern about it, we wouldn't have done it," he told BBC Sport. "We had some dialogue with Pirelli about it (before qualifying) and they didn't seem concerned, but after qualifying if you change it without the FIA's blessing you have to start from the pit lane.

"Pirelli were telling us after qualifying that our tyres were very marginal and they wouldn't say whether it was after half a lap or five laps, but they were going to fail," he continued.

"I have to say it was one of the scariest races I've been involved in," he admitted. "It was heart-in-the-mouth stuff, as first and foremost our duty of care is to the driver safety. And trying to make that call in making sure the car was safe, while not handicapping ourselves from a performance point of view, was quite a difficult judgement to make. Frankly at the end of the race I was very relieved that both our drivers were safe."

Ahead of the race, the Austrian outfit was left a stark choice, alter the camber and therefore start from the pitlane or increase tyre pressure, which reduces the risk of tyre failure, but which necessitates an earlier than normal pit stop. The team chose the latter option.

Hembery was clearly not impressed. "If you were concerned there was a safety issue with your set-up creating issues with the tyres you could have started form the pit lane, put a new set of tyres on, change your geometry and off you go."

While McLaren and Toro Rosso are also understood to have asked for permission to change their front tyres before the race, a number of teams are now said to be expressing unease that Red Bull exceeded Pirelli's recommendations in terms of camber.