SINGAPORE (Reuters) - Force India team principal Otmar Szafnauer has read the riot act to Sergio Perez, describing his erratic performance at the Singapore Grand Prix as “unacceptable” after the Mexican pushed his team mate Estaban Ocon into the wall on the opening lap.

Perez ended the Frenchman’s race after just three corners, held up Ferrari’s Sebastian Vettel and had another collision with Sergey Sorotkin’s Williams before he eventually crossed the line in 16th place after an eventful grand prix.

“You say to them that’s unacceptable, there’s enough room on the left hand side as I could see. You’ve got to give your team mate enough room,” an angry Szafnauer told reporters.

“If it’s somebody else and it’s not your team mate, it’s a racing incident. But if it’s your team mate then you’ve got to give him room.

“So we’re back to the old rules, we allowed them to race on lap one whereas in the past we didn’t allow them to race on lap one and now we can remove that.

“If they continue to do this even on lap one then there’s other ways to separate them which we hope we don’t ever have to employ.”

Perez apologized to his team over the radio soon after the safety car was deployed when Ocon crashed out, the Mexican saying he was unaware who he had made contact with during the chaotic start to a race won by Lewis Hamilton.

“It was a very unfortunate incident, one of those it is very hard to avoid,” said the Mexican, who had started seventh on the grid after a strong qualifying session.

“As I am picking up the power I just get a clip from one car -- I had not even realized that was Esteban -- and then as I get a message from the team I was very sorry for that. A very hard day for us.

“And then with the strategy we were having a tremendous first stint, opening a big gap to the car behind but then we got stuck in traffic and it was very hard to get by Sirotkin,” he added.

“Then there was contact with him. So I think we probably paid the price of a very strong qualifying, good first stint. Obviously after the race its easy to analyze and pick the right strategy but probably today we got the strategy a bit wrong.

“I don’t think I have much to say (to Ocon). I am just very sorry for the day the team had in general. I wish I could have seen Esteban there or have done something differently there.

“A tough day for us, especially after such a good day yesterday but this is racing. Hopefully, in the next couple of races we can improve and get on with better points.”