Lewis Hamilton has apologised to his McLaren team and taken the blame for his crash with Kamui Kobayshi's Sauber that ended his Belgian Grand Prix.
"After watching the replay, I realize it was my fault today 100%. I didn't give Kobayashi enough room though I thought I was past," he Tweeted.
"Apologies to Kamui and to my team. The team deserves better from me."
Team-mate Jenson Button, who came third from 13th on the grid, said "little mistakes" cost him a chance of victory.
Hamilton crashed out after colliding with Kobayashi into the braking zone for Les Combes, having just passed the Japanese driver up the hill for fourth position.
It was the 2008 world champion's second retirement of his season after a coming-together with Button in June had brought his Canadian Grand Prix to an early end.
Immediately after the incident in Spa, before revising his opinion online, Hamilton said he did not believe he was culpable for his most recent collision.
"I'm not really quite sure [what happened] to be honest," Hamilton said. "I just remember hitting the wall pretty hard.
"It's a bit unfortunate for the team, we were in a good position and as far as I was concerned I was ahead of whoever it was I was racing and then I just got hit by them and that was my race over. That's motor racing. There has been a lot of races where we haven't finished this year, so that's just another one of them."
The race stewards - who included 1992 world champion Nigel Mansell - decided to take no further action regarding the collision.
On Saturday Button had blamed a "miscommunication" with his team for his poor qualifying result, saying he chose to cool his tyres, not realising he did not have time to do another flying lap in the second phase of qualifying.
"A misunderstanding in qualifying cost us a lot of points," said Button. "If we can stop the little mistakes happening we can win races."
But following the race the 2009 world champion said that even starting from 13th he could have challenged Red Bull duo, race-winner Sebastian Vettel and second-placed Mark Webber, had his car not been damaged by debris from crashes ahead of him at the first corner of the race.
"If I'd stayed in 13th at the start it would have been easier but Turn One was mayhem caused by the guys up front," said Button, who is now fourth in the championship.
"[Paul] di Resta hit my rear wing, or we collided, it damaged my rear wing, half the endplate was gone, and then driving to Eau Rouge someone's rear wing came off and went through my front wing and took the wing mirror off, which was scary.
"I wanted to pit immediately, but the guys said we needed to keep going until lap five. We did, then put options on and then it was a case of flat out for the rest of the race.
"All weekend the car felt great, the balance has been phenomenal. So it was a case of what might have been but it was a good finish to get on the podium.
"I feel confident in the car and hopefully in Monza we can be competitive."
McLaren team principal Martin Whitmarsh said Button's qualifying disaster might have cost him the win.
"Jenson's was the drive of the day," Whitmarsh said. "If we could have got him up the front of the grid where he could and should have been he would have been a contender today."
Unlike Button, Hamilton said he did not think he would have been in a position to challenge for victory.
"I think we were struggling," he said. "For whatever reason we were massively slow on the straight, massively, massively slow and I guess that's really what got us in that position [to collide] really.
"Everyone was just pulling away from me on the straights and I was only able to keep up on the infield. I think we probably had a little bit too much downforce on. Nonetheless we were in a good position still, we were still able to challenge and I got past one of the Ferraris. We maybe have been able to have at least got a podium."