Jenson Button has defended McLaren team-mate Fernando Alonso's radio rant at the Japanese Grand Prix, saying it proves the Spaniard cares about rectifying the team's current struggles.

Alonso made headlines at Honda's home race when he branded its engine "embarrassing" and likened it to a "GP2 engine" as its power deployment issues made him a sitting duck on the Suzuka straights. Alonso and Button have put on a brave face through McLaren-Honda's for most of the year but the Spaniard's comments were taken as a sign of cracks appearing in the partnership.

The fallout meant Alonso was forced to reaffirm his commitment to staying at McLaren but Button, who recently had his contract extended into 2016, thinks it is unfair to judge drivers based on words spoken in the heat of the moment.

"It's tricky, because we're very emotional when we're driving a racing car," Button said. "It's the place where we feel the most at home and when things aren't going your way you maybe say something you maybe shouldn't say. When you say it to the team it maybe isn't a positive either but if its broadcast to the world it's very different.

"We know it gets broadcast to the world but sometimes in the heat of the moment there's so much emotion there you've got to let it out. Doing it in your helmet without the radio on feels a bit strange, you feel like you need to let people know how you feel."

Button says he and Alonso have been outspoken to Honda about its plight away from the cameras but always in a constructive manner.

"We express a lot! Just not in front of the cameras normally but there are always going to be slip-ups when emotions are running so high. Fernando and myself are pushing hard, we're not just sitting back and going through the pain.

"We probably don't normally say it like that but our comments are very useful to the team in terms of development. It hurts when you have no defence in a race, you drive round and cars can overtake you very easily after all your hard work in qualifying and at the start. You've got to try and deal with it the best you can, get out the car and discuss with the team where we need to go from there. It's important that we do have emotion because it shows that we care and we love this sport."