Jenson Button labelled McLaren's speed deficit as "painful" at the Mexican Grand Prix as the Honda engine's lack of power was again laid bare.

Button's top speed in Sunday's race was clocked at 349.5km/h, which was 17km/h slower than the fastest speed of the race recorded by Pastor Maldonado in the Mercedes-powered Lotus. For the most part, Button said the deficit was even larger, although he took some encouragement from the pace of the car in the tight final sector.

"Painful I think is the word. I was on the harder on the start but it was just waving goodbye to everyone at the start. Straight line speed they have is phenomenal. We are still doing 345kph on the straight, but they are 20kph quicker than us. So when they have DRS and full deployment they are 45kph quicker than us. It is a massive difference in speed, I couldn't hold people behind me even if I was in front of them, not that it was very often unless they were pitting or lapping me.

"At the end of the race I was behind Carlos [Sainz], which was a bit of fun and I think I was faster than the car in front for once. Again we really struggled. The interesting thing is, compared to a Williams or the middle of the pack cars we are quicker in the last sector. They come past you and in that last sector you catch them that is something to enjoy but not the result."

Most teams were able to up the speed of their turbocharger in Mexico to compensate for the loss of power caused by the thinner air at 2,200 metres, but Honda was limited in that respect.

"I think we have lost more power here than most with the altitude -- you'd think it would bring everyone closer together but it really hurt us here," Button added. "Hopefully Brazil will be better and Abu Dhabi, then we can enjoy the winter."