The Haas driver pulled out his mobile phone to show footage to reporters at the Austrian Grand Prix to back up his grievance.
"That's my onboard (camera). Tell me what I did wrong?" he said. "That's how you get a five-second penalty. Did I move my steering wheel? Did I turn to the left, did I do anything?
"It's absolutely nonsense. That's all I can say ... I couldn't know he (Force India's Ocon) was here because I'm almost on the edge of the track so I'm not expecting a car to be there.
"I think they were drinking rose wine instead of ..." he tailed off.
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Grosjean said he had sent his compatriot a text apologising for not having seen him on the track, although he felt it was just a racing incident.
The Force India driver had not responded, and Grosjean said Ocon had not raised the subject when they flew in together earlier on Thursday.
"It was our French Grand Prix and everyone wanted to do well," he said.
"I think my penalty is nonsense ... I got the video this morning and when I saw it I was pretty shocked. Having got a penalty for that."
The Frenchman was already feeling the frustration before the race at Le Castellet, where he finished 11th, after having failed to score a point so far this season in a barren run that extends back to last year.
Only one other driver, Russian rookie Sergey Sirotkin at Williams, has yet to open his account this year.
Grosjean has now gone 12 races without a point, but he said it was still not as bad as his 2012 season with Lotus, when he endured a number of collisions at the start.
Australian Mark Webber famously dubbed him a "first-lap nutcase", a particularly stinging insult for a driver who subsequently used a sports psychologist to regain his confidence.
"It was a tougher time than it is now," he said.
"It's not easy right now, and obviously we want more for the team, but if you look at all the races, some I could have done much better and some others it's just circumstances."
(Reporting by Alan Baldwin; editing by Andrew Roche)
