McLaren yesterday came out fighting following stinging criticism from technical analyst Gary Anderson.
BBC pundit Anderson, who worked as technical director at Jordan and Stewart Grand Prix from 1991-2003, ripped into McLaren following practice for the Canadian Grand Prix.
Jenson Button spent the majority of the second 90-minute session stuck in the garage as mechanics feverishly worked to repair an oil leak and twice replace the gearbox.
That prompted Anderson to launch a rant against McLaren as he said: "I want to say something about McLaren and the problems with Jenson Button's car.
"This is a top team with a world champion in it challenging for the world championship.
"They're changing the gearbox - it should be 30 minutes. It's not good enough.
"During that time Caterham rebuilt the car of Heikki Kovalainen, who hit the wall."
McLaren managing director Jonathan Neale, however, vigorously defended the team, notably highlighting the complexities of a modern-day F1 car.
Neale said: "The packaging is so extreme that to take off a gearbox and put it on again routinely takes, on average up and down the grid, an hour and three quarters.
"Bear in mind to even start a Formula One car from a laptop from cold these days takes an hour and a half. It's not as trivial as some might have you believe.
"So we changed the seal in between FP1 and FP2, got the car back together, got the floor on, fired it up and discovered we then hed a secondary issue which wasn't knowable prior to that event.
"So it all had to come off again and we had to do two gearbox changes.
"There wasn't time to delve into the root cause, so we changed the back end of the car, which was another hour and three quarters.
"We apologise to Jenson for the unreliability, but we're back on it and I'm confident we've a good car, as Lewis Hamilton has attested and we'll be back on it tomorrow."
Button, who has fallen 31 points behind title leader Fernando Alonso in his Ferrari after three poor weekends in which he has collected just two points, unsurprisingly put on a brave face.
"These things take a long time," said Button, who managed 14 laps in the final 19 minutes, finishing half a second behind team-mate Lewis Hamilton.
"We eventually got out with 15, 20 minutes to go and fair play to the guys for getting the gearbox back on so we could get some laps in. They worked flat out all day.
"We have some data, so hopefully we can look at that and make some good improvements.
"We can still have a good weekend, we're still positive. The car is quick as Lewis proved, he did a good job and was very fast, so I'm not worried."
Hamilton underlined what was possible as he finished quickest at the end of both sessions, with his best lap a one minute 15.259secs.