Lewis Hamilton was subjected to racist abuse by spectators at the Montmeló circuit near Barcelona on Saturday, leading to the Spanish motor racing authority being warned by the FIA that any repeat would have serious consequences. At the same time, it has emerged that the British driver's reputation was tarnished unfairly last season when he was widely reported to have sworn at Ron Dennis, the McLaren principal, over the team radio.

Hamilton has been taking part in a three-day official Formula One test at the Spanish circuit, which finished yesterday. According to local media reports, he was booed and abused each time he walked from the McLaren team's motorhome to the garage on the pitlane on Saturday.

Eventually, circuit staff erected fences to protect him from view and removed offensive banners that had been put up opposite the team's base. Many of the spectators present were supporters of Fernando Alonso, the Spanish driver with whom Hamilton had a dramatic falling-out last year when they were team-mates at McLaren. Alonso has since returned to Renault.

The relationship between Hamilton and Alonso reached its nadir at the Hungarian Grand Prix last August. The British rookie was denied a chance of pole position at the Hungaroring after Alonso appeared to have deliberately delayed him in the pits. This left Hamilton insufficient track time to complete a final lap and he was alleged at the time, in remarks that were carried in newspapers all over the world, to have lost his temper as he crossed the finish line at the end of the highly charged qualifying session.

However, The Times has established that the episode was misreported and that Hamilton showed admirable restraint. In fact, it was Dennis who swore, not his young protégé.

“Don't ever f***ing do that to me again,” Hamilton was reported to have shouted to Dennis as he crossed the finish line. Dennis was then alleged to have replied: “Don't ever f***ing speak to me like that again!” At this point, Hamilton was supposed to have uttered the words: “Go f***ing swivel!”

The reporting of the altercation, based on leaks from an engineer at Renault, led to widespread criticism of Hamilton. He was condemned as an arrogant upstart who did not know his place. The Times can reveal, however, exactly what was said that day and, based on authoritative sources, can show that a very different conversation occurred, and that the exchange was to have a far bigger impact on the weekend's events than was known at the time.

As he drove across the line, Hamilton, adopting an ironic tone, said: “Thank you, guys. Thank you, that was great.” Dennis then replied: “That shows what happens when you don't f***ing do what you're told!” The infamous comment about “swivelling” was never uttered by Hamilton.

At the time, the exchange was viewed as evidence of how heated matters had become between Hamilton and Alonso. What was not known was that the stewards at the Hungaroring relied heavily on it when they decided to penalise McLaren. The team lost their constructors' championship points for that weekend, while Alonso was demoted five places on the grid for the next day's grand prix.

In their investigation, the stewards were looking for evidence that McLaren had assisted Alonso in deliberately balking Hamilton. Reviewing recordings of the radio traffic between the team and their drivers, the stewards took Dennis's remark to mean that Hamilton had indeed been punished for disobeying team orders.

An odd feature of the affair is that, given that they relied so much on the short conversation between Hamilton and Dennis, the stewards did not publish it at the time to help to explain their findings. For their part, McLaren initially gave notice that they would appeal against the loss of points, but later the team decided to accept it.

Hamilton did not comment on the abuse he suffered in Spain on Saturday, but Indy Lall, the McLaren test team manager, condemned the attacks. “It is not right the way he is being treated,” he said.

Ramon Pradera, the circuit manager at Montmeló, where the Spanish Grand Prix will be held at the end of April, appealed to fans to “behave correctly”, adding that “no type of offensive behaviour can be tolerated”. A spokesman for the FIA, the sport's governing body, said that racism in Formula One was unacceptable and warned the Spanish authorities about any repetition of such behaviour.