The International Automobile Federation (FIA) says Spanish circuits risk punishment after claims Lewis Hamilton was racially abused at testing.
Last year Hamilton and Spanish McLaren team-mate Fernando Alonso had a tense relationship, and he was allegedly taunted by Circuit de Catalunya fans.
“We are surprised and disappointed at the abuse,” said an FIA spokesman.
“This is a clear breach of FIA principles and any repetition will result in serious sanctions.”
Reports in a number of Spanish papers said the 23-year-old Briton was booed and insulted whenever he made his way from the team motorhome and into the pits on Saturday at the Barcelona circuit.
Some had blacked up their faces
“It is not right the way he is being treated,” McLaren test team manager Indy Lall was quoted as saying.
BBC Radio 5 Live’s Formula One commentator David Croft explained that some of those present to watch the testing had gone to great lengths to upset the British driver.
“There were about 55,000 fans present over the three days of testing,” said Croft.
“Some had blacked up their faces while some had T-shirts misspelt with Lewis Hamilton’s family featured on the front.
“They were chanting nasty stuff and booing him when he made his way from the garage to the McLaren area at the back. We’ve never seen that at Formula One events.
“The offcials at the circuit drafted in extra security guards to the stands and put some fences around the team area.
Croft added: “They have pleaded with fans not to repeat that behaviour again.”
This year Spain will host two Grands Prix this year, the Spanish race in April at Circuit de Catalunya, and the European Grand Prix on the streets of Valencia in August.
Valencia’s Ricardo Tormo circuit and Jerez are also used for pre-season testing.
Although the FIA did not spell out the sanctions, either circuit could lose its place in the championship if local organisers fail to deal with any further incidents of racist behaviour.
“We would like to make a plea to the fans to behave correctly, no type of offensive behaviour can be tolerated,” circuit director Ramon Pradera was quoted as saying in La Vanguardia newspaper.
The McLaren team did not issue any formal comment on the allegations.