Racing Point have been docked points and fined 400,000 euros (£361,000) for illegally copying parts of last year's Mercedes car.
The ruling came following a protest by Renault against the 2020 Racing Point, arguing that they had copied the brake ducts used by Mercedes in 2019.
F1's governing body the FIA upheld the protest in part and have also deducted 15 points from Racing Point.
Racing Point can appeal but have not indicated whether they will.
The ruling hangs on the stipulation in the rules that teams must design specific parts of the cars themselves.
Renault argued that the front and rear brake ducts of the Racing Point were too similar to those on the 2019 Mercedes to fit this description and that the information could not have been obtained other than by a transfer of intellectual property.
Brake ducts are key parts in the aerodynamics of an F1 car, as they help control the airflow off the front wing, increasing downforce.
Mercedes admitted they had supplied information about the front and rear brake ducts of their 2019 car, but this was allowed because these were not listed parts at the time.
The FIA decided that the front brake ducts of the Racing Point were legal as, although they had been copied from Mercedes, they had been used on the 2019 car.
But a rule change between 2019 and 2020 added brake ducts to the category of so-called "listed parts" that teams have to design themselves.
Stewards found that Racing Point had used computer design data legally supplied by Mercedes to Racing Point in 2019 to design their rear brake ducts with "minimal changes" and fit them to their 2020 car.
As the parts had not been used on the 2019 car, they were not permitted to be used in 2020, because they were a Mercedes design, not Racing Point's, and had not been an integral part of last year's car.
The FIA said that had Racing Point asked whether they could use the 2019 Mercedes rear brake ducts on their car this year, they would have been told they could not. But they did not ask whether this was allowed.
And the FIA found that "on a fair reading" of the rules, the rear brake ducts on the 2020 Racing Point "were designed in large part by Mercedes".
The FIA found that Racing Point "minimised the significance of the input it received from Mercedes and overstates the amount of work it actually did. Mercedes gave Racing Point a large proportion of their brake duct designs. Racing Point then made relatively minor changes to them."
The protest covered the first four grands prix of the season, and the FIA stewards said the points deduction was "intended to penalise the potential advantage Racing Point may have accrued in the design process".