Haas driver Romain Grosjean was disqualified after the Italian Grand Prix. File picture: Luca Bruno / AP Photo.

Monza - French driver Romain Grosjean was disqualified from the Italian Grand Prix on Sunday after stewards upheld a Renault protest against the legality of his Haas car.

Grosjean had finished sixth in the race, sending Haas ahead of Renault in the constructors standings.

The disqualification, which is subject to appeal, meant the French carmaker stayed fourth while Force India's Esteban Ocon was promoted to sixth in the race.

Force India's Sergio Perez moved up to seventh, with Renault's Carlos Sainz eighth and the Williams pairing of Lance Stroll and Sergey Sirotkin ninth and 10th.

The point was Sirotkin's first in Formula One.

The governing FIA said in a long explanation of the ruling that Renault had argued that Grosjean's Haas did not comply with a technical clarification issued to teams in July.

All teams had been given until Monza to comply but Haas had not done so, with Renault presenting photographic evidence to back their case.

US-owned Haas had provided details of a new solution in an email exchange with the FIA but had asked for more time to implement it, given the August break.

"We will endeavour to introduce this upgrade for the Singapore GP, but will be somewhat at the mercy of our suppliers so we would request some flexibility in this matter," the team wrote in an email.

Haas had thought its solution and timing request had been accepted but the FIA said its head of single seater technical matters had warned the team that it risked a protest if the car was not corrected by Monza.

"While the Stewards are also sympathetic to the difficulties of producing these parts, the Stewards noted that at least one other competitor was able to comply in the time provided," the statement said.

"Further, it was made clear to the competitor from the outset that the FIA Technical Department did not consider their car to be in compliance, and further that they left themselves open to the circumstances they now find."

The stewards ordered Grosjean to be disqualified from the results and the classification amended.