Red Bull technical guru Adrian Newey says he is baffled by engine partner Renault's attitude after a disappointing start in Melbourne.
The 2013 world champion team struggled in pre-season testing last year, with the Renault power unit proving highly unreliable and no match to leaders Mercedes in terms of power.
Although Renault made progress throughout the season, the Mercedes-engined cars dominated often.
Winter testing ahead of this weekend's Australian Grand Prix showed Mercedes was still the dominant force, and the best Renault qualifier on Saturday was Red Bull's Daniel Ricciardo down in seventh place, two seconds off pole position.
In the race, Daniil Kvyat did not even make it to the grid, while Ricciardo finished down in sixth, one lap down.
Earlier this week, Red Bull advisor Helmut Marko was critical of Renault for its lack of performance, and now Newey has added his voice to the criticism, saying the French manufacturer is not willing to engage with Red Bull in order to make progress.
"It's very frustrating that we've been pushed into a position where we've got an engine which is quite a long way behind with no obvious light at the end of the tunnel with all sorts of failings," Newey told the Telegraph.
"We keep trying to offer help and try to be involved but there seems to be a real reluctance to engage. It's one thing being in the position where you're not competitive but you can see your way out of it.
"It's another thing when you're not competitive and your partner doesn't seem to be willing to engage. I honestly don't know the reason for it."