Fernando Alonso has said that there is nothing wrong with the McLaren car or his own driving.
The Spaniard was happy with his qualifying lap in Montreal, saying that it equated to pole when the Honda power deficit was factored in.
Amid rumours that Honda is 90-100 horse power down, Alonso told Auto Motor und Sport: "I don't want to say numbers because I cannot prove them.
"But if you look at the time we lose on the straights, we would be very competitive."
The German report said that McLaren have calculated with GPS that they are losing 1.3 seconds around Montreal due to Honda.
"With a top engine, we could have done [Valtteri] Bottas's time," an unnamed team member said. "Only Vettel and Hamilton would have been out of reach."
McLaren's new, highly critical tone is reportedly the result of Honda having promised and then failed to deliver a key engine upgrade for Canada.
"It's wrong to talk about a delay," boss Yusuke Hasegawa said. "We would have liked to have it in Canada, and now we hope to have it in Baku, but I cannot promise."
Some suspect that McLaren have already decided to dump Honda, but boss Eric Boullier said: "We have a long-term contract with Honda and are connected on many levels.
"I hope there is still a McLaren-Honda next year, as we want to believe in this project. But at the moment our patience is put to the test."
Indeed, there are now clear signs of strain even in the personal relationships. McLaren executive Zak Brown said this week that Honda is "lost".
"It was an unfortunate word," said Hasegawa, according to Spain's AS newspaper.
Brown replied: "I do not think I said unfair or unfortunate things, and I get along well with Hasegawa-san.
For now, therefore, McLaren are not ruling out splitting with Honda and entering talks with Mercedes, Renault or even Ferrari.
"We value all our options, and the whole situation is very complex with sporting but also commercial aspects, so it is not something simple," Brown said.
"But we will have an engine in the car next year."
McLaren are still searching for their first points of the 2017 championship.
