BUDAPEST (REUTERS) - Renault's Nico Hulkenberg of Germany branded Haas rival Kevin Magnussen the "most unsporting" driver in Formula One after a Hungarian Grand Prix clash between the two on Sunday.

Hulkenberg had been frustrated by the Dane forcing him off as he tried to pass at turn two in the closing stages of the race.

The Renault driver retired in the pits while Magnussen collected a five-second penalty but finished 13th.

"When it comes to racing, he's just nasty," said Hulkenberg, who "congratulated" Magnussen in front of TV reporters in an angry exchange that turned the air blue when the Dane replied.

"Hard defending is fine, but what he does is just ruthless and sending people into the wall."

Magnussen had earlier criticised Hulkenberg over the team radio for an incident involving his French Haas team-mate Romain Grosjean.

"If you can do what Hulkenberg did to Romain, then it's going to be a dirty race," he said.

Haas team principal Guenther Steiner defended Magnussen, calling Hulkenberg a "bully".

"He got away a long time with it and maybe now it's time that somebody stands up to him," he added.

"He's a good driver, he doesn't need to be like this."