The 2018 Haas (left) alongside the 2017 Ferrari

Haas boss Gunther Steiner has rejected accusations that the team's car is an illegal copy of last year's Ferrari.

McLaren driver Fernando Alonso and Red Bull boss Christian Horner have voiced their complaints while the Force India team are also unhappy.

F1 rules dictate that teams must design their own chassis and aerodynamics.

But Steiner told BBC Sport the critics "talk without intelligence and without knowledge" and invited them to lodge a protest if they have a problem.

Governing body, the FIA, gave Haas the all-clear at the season-opening Australian Grand Prix last weekend.

FIA's F1 director Charlie Whiting said he had no concerns about the relationship with Ferrari, saying: "We know exactly what's going on between Haas and Ferrari, which is completely legal. Last year we had one team expressing some concerns but we have not seen anything that concerns us at the moment."

Why are rivals unhappy?

Haas' drivers were on course to finish fourth and fifth in Melbourne before they were both forced to retire

Haas have caught the attention of rivals at the start of the 2018 season, partly because their new cars have been surprisingly competitive.

Drivers Kevin Magnussen and Romain Grosjean qualified sixth and seventh in Melbourne and were on course to finish fourth and fifth in the race before they were forced to retire within two laps of each other after they were sent out from pit stops with wheels not properly attached.

But the debate goes to the heart of the concept of what an F1 team is.

The concerns of their rivals are that Haas' approach undermines the ethos that teams have to be constructors in their own right, as well as bringing their own business model - and potentially viability - into doubt.

Rivals' concerns centre on two major issues: the apparent resemblance between parts of the Haas car and the Ferrari, particularly last year's car from Maranello; and how Haas can design such a competitive car with the smallest workforce in F1.

How do Haas run their team?

Haas buck the trend of most F1 teams in buying more than just their engine from other manufacturers

Haas, owned by American businessman Gene Haas, are unique in buying as many parts from another team as the rules allow them - in this case Ferrari - and designing only the minimum required themselves - the monocoque and aerodynamic surfaces.

Everything else - the suspension, gearbox, engine, hydraulics, electrics and electronics - is bought off the shelf from Ferrari.

Other private teams tend to buy only engines from manufacturer teams. Force India go as far as buying the engine and gearbox from Mercedes but do everything else themselves.

What is Haas' view?

Steiner said he had heard the criticism but said they had no foundation.

"They see ghosts," he told BBC Sport, adding that those making the remarks "didn't understand car design".

"(They say): 'The car looks very similar to a Ferrari from last year.' So should we have copied their car, which is behind us, or should we go with a car that goes pretty quick? Give me an answer to that."

Steiner also said that it was not possible for the 2018 Haas to be a wholesale copy of the 2017 Ferrari because the two cars had different size wheelbases, and the wheelbase and suspension define the positioning and shape of a lot of the aerodynamic surfaces.

The current Haas is forced to have a longer wheelbase than last year's because it uses the 2018 Ferrari suspension, and the 2018 Ferrari is longer than the 2017 Ferrari.

Steiner maintains there are several differences between their car and Ferrari's 2017 model

"We have got the same (wheelbase) as Ferrari. We have to because we have the same suspension - why would we do it different?" Steiner said. "It's logic. So it cannot be last year's Ferrari because it has the same wheelbase as this year's Ferrari.

"My point is, if they have got a problem with that, I show them the way to the FIA. They can file a protest."

Steiner believes the complaints were based on the fact Haas were in front of the teams who were most vocal.

"If you have to justify your incompetence, attack is the best defence," he said. "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."

Haas has only 220 employees, compared with nearly 600 at Williams, about 400 at Force India and nearly 700 at McLaren.

Steiner says the fact they do not need to design and test as many parts as other teams explains how they can produce their car with so few people.

He said the team's aerodynamic design work is done in-house, while any mechanical design required is sub-contracted from Italian race car constructor Dallara.

McLaren racing director Eric Boullier said: "There are rules in place and we have to trust the governing body that everyone is doing his job properly.

"It is true they have made a significant gain in terms of performance. They are not a big team and they are very close to Ferrari. Some parts of the car might look very similar but maybe it is a coincidence."