Hamilton trails Robert Kubica in the drivers standings by four points
Kimi Raikkonen was left cursing his luck after a "stupid" pit-lane mistake by Lewis Hamilton ended his race at the Montreal Grand Prix.
The Briton ran into the back of the Ferrari driver as the Finn waited at a red light to rejoin the race.
Both drivers retired but Hamilton faces a further cost of being demoted 10 grid places at the French Grand Prix.
Raikkonen said: "I'm not angry but what Hamilton did was inexplicable. More, it was stupid."
Hamilton had no argument with the punishment by Formula One's governing body, the FIA, and McLaren confirmed they will not be appealing the decision.
The Englishman will head to Magny Cours on 22 June having lost his championship lead to BMW Sauber's Robert Kubica who recorded his first Grand Prix win during an eventful race in Canada.
I apologise to Kimi if I ruined his race. I would rather neither of us be out
And the incident meant Raikkonen has failed to score points in his last two Grands Prix after the Finn drove into the back of Adrian Sutil's Force India in Monaco two weeks ago.
Raikkonen added: "I'm not the right person to talk about a shunt, given what happened in the last race but it is one thing to collide on the track in the heat of the race and another in the pit lane when you are stopped at a red light."
The punishment capped a weekend turned sour for Hamilton, who had qualified in pole position and was seemingly on his way to back-to-back wins in Montreal.
The McLaren driver had built up a 6.8-second lead over Kubica before the safety car emerged on lap 17 following Sutil's crash.
When the pit lane reopened two laps later, Hamilton took on board enough fuel to see him through to the end of the race.
But in his hurry to get back out, and not lose sight of Raikkonen and Kubica who had both refuelled first, he ran into the back of Raikkonen.
Raikkonen and Kubica had been lined up side-by-side waiting for the pit lights to turn green, signalling that they could return to the track.
"I saw the two guys in front of me battling in the pit lane and all of a sudden they stopped," explained Hamilton, 23.
"I saw the red light but it was too late to stop. I don't think it's a racing incident. It's just unfortunate when this stuff happens.
"It is a lot different if you crash into the wall and you are angry with yourself.
"I apologise to Kimi if I ruined his race. I would rather neither of us be out. I was so quick I was breezing it.
"We'd looked so strong for the whole weekend though, so at least we can leave Montreal confident that we have a package that will enable us to fight for the world championship from here on in."
It's difficult for a driver to decide whether to focus on the lights or on the cars ahead in situations like that
McLaren boss Ron Dennis on Hamilton's crash
Kubica, meanwhile, was happy to emerge unscathed from the incident.
"We all pitted together," said the Pole. "I saw Kimi side by side with me.
"Then I just heard a big shunt and saw Kimi's moving and realised it was Lewis. He was over Kimi's rear wing.
"I just kept concentrating waited for the green light and managed to pull away well.
"I have to thank him that he shunts Kimi and not me."
McLaren team principal Ron Dennis defended Hamilton's error but was keen to put a dismal weekend behind him as the team aim to recapture the lead in the drivers' championship.
"No racing driver would deliberately put himself out of a Grand Prix, and the plain fact is that Lewis didn't realise that the cars in front of him were coming to a halt until too late," Dennis said.
"It's difficult for a driver to decide whether to focus on the lights or on the cars ahead in situations like that.
"For a team that exists to win, today was a very disappointing day. But the fact is that we had the pace and therefore the capability to win, which is of course encouraging."