Jenson Button has admitted that "it hurts" seeing McLaren so far off the pace ahead of the Belgian Grand Prix.

The Englishman will start at the back of the grid, alongside teammate Fernando Alonso, and claimed that there is "a long way to go".

He told reporters: "I actually enjoyed driving the car, and when you cross the finishing line and you see the time you think 'That's not bad'. But then when you see where you are, a second off the guy in front of you, it's a massive margin, it hurts.

"That's puzzling and disappointing, and shows there is a lot of work needed to close that gap, and a long way to go before we feel happy with the package we have.

"There's definitely more power with the engine at least, but you always want more than you see, and we're still a long way off."

Lewis Hamilton will start on pole for the race, ahead of Nico Rosberg.