Sebastian Vettel boos are unfair, says Red Bull's Christian Horner
Red Bull team boss Christian Horner says it is "unfair", "not right" and "not deserved" for fans to continually boo Sebastian Vettel.
The German was booed again after winning the Singapore Grand Prix - as he has been at virtually every race since Canada apart from his home event.
Horner said: "It's so unfair. It's not sporting. The boy has driven an unbelievable race.
"Of course he says it doesn't affect him, but he's a human being."
Fans give a number of reasons for booing Vettel, but one of the prime ones is his ignoring of team orders not to pass team-mate Mark Webber to win the Malaysian Grand Prix early this season.
His continued domination of F1 is probably another. Singapore was his third consecutive win, his seventh in 13 races this season and he is well on course for his fourth consecutive drivers' title.
"Standing up on the podium what you see is there is a small collective group [who start it off] and then it's a like a pantomime, it ripples off," he said.
"I don't know what [the reason] is. For sure Malaysia didn't help. But it's happened. It's been done. There's been an awful lot written about it and there were circumstances that were involved in that that Sebastian felt [he was doing the right thing].
"When you have a guy who almost becomes a serial winner, it's like people when they watched Muhammad Ali, people want to see who's going to beat him and it's a little bit like that now.
"So when he keeps wining maybe it isn't the most popular result but it's not sporting and not fair not to recognise when a sportsman has delivered in the way he has.
"He's a great kid. He has a great sense of humour, a big heart. And of course he's ambitious. He's a competitor and he will push. He enjoys winning and it's a shame. And I hope it will change in the forthcoming races."
Horner was backed by Mercedes executive director Toto Wolff, who said the continued booing was "a shame - he's a well-deserved world champion".
Vettel said he believed the boos were largely from Ferrari fans upset that he continues to beat Fernando Alonso, who was second in Singapore and is his closest title rival, albeit 60 points behind with six races to go.
Vettel said: "It's not nice but I think you should look around the grandstands.
"Most of the fans are dressed in red, Ferrari has a very strong fan base for a reason: they have a lot of tradition in Formula 1, they've been around longer and won, and they've been more successful than any other team.
"There's more and more people dressed in blue [supporting Red Bull] so we are doing a good job on that front. But obviously they are quite emotional when they are not winning, and if somebody else is winning they don't really like it.
"As I said, they are on a tour and they come back to [each race].
"They are wealthy enough to go to a lot of races, Monza or take the flight to come here to Singapore.
"As long as they keep booing, we are doing a very good job so that's the way I see it.
"It's not people from Singapore or from one country only.
"It's normal in sports if some people support one driver then they don't like another driver to win.
"Equally there were a lot of German flags around the track, there are a lot of Germans here in Singapore, it's a very international city.
"The parade lap was quite nice and also the lap after the chequered flag there were a lot of people cheering.
"Obviously I didn't give them the most exciting race but on days like this I really don't mind."