McLaren managing director Jonathan Neale has defended his team against BBC technical analyst Gary Anderson's criticism.
Anderson, who worked as technical director with Jordan and Stewart Grand Prix from 1991 to 2003, was less than complimentary regarding a gearbox issue with Jensen Button's car that effectively wrecked his practice session ahead of Sunday's Canadian Grand Prix.
The British driver was forced to spend most of the second session watching from the sidelines.
"This is a top team with a world champion challenging for the world championship," said Anderson.
"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 discovered they hadn't fixed an oil leak, and they had to change the gearbox, but that should be a half-hour job.
"If you're trying to win the championship, you can't afford to make mistakes like this."
Neale explained what happened however, hinting that Anderson appears to be out of touch with a modern-day F1 car.
"You have to go back to FP1," he said.
"As Jenson came out of the last corner on his final run he felt he had a lot of wheel spin, which turned out to be clutch slip.
"After getting the car into the garage and taking it apart we found oil contamination of the clutch which causes the plates to slip. Clearly it was something we had to address.
"The oil was coming from the gearbox through one of the seals, which we would routinely change.
"But the problem these days, if you take a modern gearbox on a Formula One car, they, and the powertrain in particular, are so integrated now.
"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.
"So 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 had 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 eventually finished half a second down on Hamilton, who was quickest throughout the two sessions, with a best lap-time of 1:15.259.