|Italian Grand Prix on the BBC|
|Venue: Monza Dates: 4-6 September|
|Coverage: Highlights on BBC TV, coverage on BBC Radio 5 live, online, mobile, the BBC Sport app and Connected TV. Full details here|
McLaren driver Fernando Alonso has revealed the extent to which engine partner Honda is responsible for the team's lack of pace this season.
The McLarens qualified 16th and 17th, with Jenson Button 0.096 seconds ahead of Alonso but 2.661secs off Lewis Hamilton's pole position for Mercedes.
Alonso said: "On a circuit that has six corners, on the GPS, we lose two or three tenths in those corners.
"The rest of the three seconds, we need to find on the straights."
The two-time champion's remarks are the first official explanation from McLaren-Honda as to exactly how the pace gap to the front is split between the team's car and engine.
It confirms information from insiders that the car is pretty competitive - among the four fastest chassis along with Red Bull, Mercedes and Ferrari - but that the engine is a long way down on power.
Insiders say that the Honda at its best is at least 100bhp down on the Mercedes - and that the hybrid element of the power-unit, which accounts for 160-180bhp of the total power of the engine, runs out of boost part-way down all but the shortest of straights.
That means the McLaren-Honda is lagging nearly 300bhp behind the Mercedes for a significant proportion of the straights on the Monza track, and is by some measure the worst engine in F1.
Honda returned to F1 this season for the first time since pulling their factory team out at the end of 2008.
The company have struggled to come to terms with the complex hybrid engines introducing in to the sport in 2014.
In its defence, it has been pointed out by McLaren that while Mercedes started developing its engine as long ago as 2010 for introduction in 2014, Honda did not start work on its unit until the early part of 2013.
Alonso, who joined McLaren this year on a three-year deal worth $40m (£26m) a year, insists that he remains confident Honda will become competitive in the end.
"Every day we do so many interviews and so many of them are so negative because we are out of Q1 and we are so slow," he said.
"This is a work in progress. We don't take every weekend as an opportunity or a look in the times and the position. We know we are last. It is frustrating for everyone in the team but it is a period we have to go through together.
"We are moving in the right direction. We'll see how long we need to be competitive and how long I will stay in F1."
Alonso's former team Ferrari, who he left at the end of 2014 two years before the end of his contract after negotiating an early release, qualified second and third at Monza.
But when it was suggested to him he might feel embarrassed at his decision because Ferrari were doing so well, Alonso told BBC Sport: "Well, doing well is relative - compared to who?
"Compared to us they are doing really well, but compared to what we did in the five years we were together they are not doing anything better.
"We were leading the championship a couple of years here in Monza. Now they are third, 100 points behind the Mercedes. Congratulations to them but they should not be happy being 100 points behind Mercedes.
Honda F1 boss Yasuhisa Arai admitted that the deployment of the hybrid system was the biggest problem.
"We have already found what is the weak point of the power-unit and we have already started work on it," he said.
He said the biggest part of that work would happen for 2016 but that Honda hoped to add small improvements to the hybrid system during the remaining seven races of this season.