But Newey says Red Bull must also take the blame.
"What stopped us at Jerez - on our side as opposed to Renault - was a problem where the bodywork local to the exhaust was catching fire," he is quoted by the Daily Star.
"It was really a lack of time. It was something we could have proved out on the dyno if we had managed to get everything together earlier.
"But Renault have been up against it in terms of their use of the dyno; we have been up against it making the parts in time," Newey added.
"So had we been a couple of weeks further ahead then that could all have been done in private on the dyno. But unfortunately it was done in public.
"Hands up on our side, that was a Red Bull problem," the Briton said.
With both Red Bull and Renault taking fixes to this week's Bahrain test, world champion Sebastian Vettel will be first at the wheel on Wednesday and Thursday.
And the last two days of the initial Bahrain test will be conducted by the German's new teammate, Daniel Ricciardo, Red Bull confirmed.