Kiwi driver Brendon Hartley's Formula One career wasn't the only thing left hanging by a thread after a nasty spat with teammate Pierre Gasly put the pair's relationship in doubt during the Brazilian Grand Prix.

Following one of his best starts of the season, a points finish for Hartley looked promising and with Renault of Carlos Sainz in his rear-view mirror Hartley asked Gasly to let him pass.

But after his Toro Rosso teammate repeatedly refused to comply, Hartley couldn't hold back his frustration.

"I'm getting pretty close to Gasly, guys," Hartley said over the team radio.

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"What's going on, guys – I'm going to get caught by [Carlos] Sainz, if you don't let me past Gasly.

"Is he gonna let me by? What the f**k is going on? He is holding me up so much."

Hartley was then suggested by his engineer to get closer to Gasly after failing to pass at corner four but the 29-year-old exploded.

Brendon Hartley of New Zealand driving the (28) Scuderia Toro Rosso STR13 Honda leads Sergio Perez of Mexico driving the (11) Sahara Force India F1 Team VJM11 Mercedes. Photo / Getty
Brendon Hartley of New Zealand driving the (28) Scuderia Toro Rosso STR13 Honda leads Sergio Perez of Mexico driving the (11) Sahara Force India F1 Team VJM11 Mercedes. Photo / Getty

"Mate! I'm right up his f***ing ass," he yelled. "What is happening here, guys?

"I am not attacking him, because he is supposed to be letting me by, but then he doesn't do it."

Eventually, Gasly allowed his Kiwi teammate to pass but Hartley was unable to clinch the final points-scoring place behind India car of Sergio Perez.

Hartley has since apologised for his outburst expressing his frustration over the situation.

"Sorry about the language on the radio, guys," he said. "I wasn't trying to race him, which Is why I was getting so upset."

"It's annoying you don't get to score points as a reward, but there weren't any retirements at the front to capitalise on.

"I felt this was one of the best performances of my F1 career but without the reward of points. The team will work hard over the next weeks to understand why we had such good race pace in Mexico, but struggled two weeks later here in Brazil."

After 20 races this year, Hartley has managed just four points to rank 19th on the ladder with his best finish a 9th placing.

Toro Rosso bosses have since put immense pressure on the Kiwi driver, demanding a strong finish or risk his place in the 2019 season.

Meanwhile, Hartley wasn't the only driver to let the pressure in Brazil get to him.

Max Verstappen was left furious after being denied a famous victory over Lewis Hamilton.

Verstappen was surging clear of Hamilton when he and the Force India collided. It allowed Hamilton to pass Verstappen and win the race.

After calling Ocon a "f***ing idiot" over the radio, the young Dutchman then told his team: "I hope I can't find him now in the paddock because that guy has a f***ing problem."