Team bosses at McLaren and Force India have called into question Haas' relationship with Ferrari after the American team's strong performance during the Australian GP.

Kevin Magnussen and Romain Grosjean were the surprise leaders of the midfield during the opening weekend of the new Formula 1 season, claiming fifth and sixth on the grid in qualifying with Magnussen running fourth early on after passing Max Verstappen at the start.  

Their pace though has led to some ponder just how far Haas' technical partnership with the Scuderia goes, particularly given the VF-18's resemblance to the 2017 Prancing Horse.

"I don't have any evidence to suggest Haas is not operating within the rules," McLaren executive director Zak Brown told Motorsport.com. "[But] we all know they have a very close alliance with Ferrari and I think we just need to make sure it's not too close.

"There could be some influence, there's certainly some parts of the [2018 Haas] car that look very similar to last year's [Ferrari] car. But that's for the engineers and the FIA to look at more closely."

His comments follow Force India COO Otmar Szafnauer admitting his scepticism at the design of the new Haas. What he also conceded, however, was deciding whether any copying had taken place would be very difficult. 

"I don't know how you can tell unless you start investigating," he said. "Scrutineering only tells you that it fits within the boxes of the regulations.

"Is it yours or somebody else's [idea]? That's the real question and I don't know the answer to that.

"Maybe it is their own, it's just suspect - how can you gain that knowledge without history and the right tools and people?"

Haas team principal Guenther Steiner has brushed off the questions around the team's car though, believing the noise being made by McLaren and Force India is due to those teams being behind them.

"If you have to justify your incompetence, attack is the best defence," he told the BBC. "If somebody has double the amount of money and is behind us, whoever owns the team should be asking, 'what are we doing here?'

"It's competition. Maybe next year we are last. When you speak, you need to have an argument you can back up, not just assumptions."