Force India team boss Otmar Szafnauer has imposed immediate restrictions on Sergio Perez and Esteban Ocon after the pair collided at the start of the Singapore Grand Prix.Needing all the points they can get after returning to zero following the mid-season takeover by Lawrence Stroll, the Silverstone-based squad made the perfect start with two double top-10's at Spa and Monza.That competitiveness continued at a very different type of circuit at Marina Bay thanks to a significant number of upgrades but it all went wrong as Ocon tried an adventurous move around the outside of his teammate at Turn 3.A clash was inevitable with Perez pitching the Frenchman into the wall on the exit and though the stewards deemed it a racing incident, Szafnauer had no hesitation in introducing team orders.“It’s unacceptable for them to come together like that in an area where there’s no run-off room. If it’s your teammate, you’ve got to give them room," he told Sky Sports appearing to pin blame on the Mexican.

Offering his view of the clash, Perez added: “It was very unfortunate, one of those which is very hard to avoid.

“As I’m picking up the power I get a clip from one car, I didn’t even realise that it was Esteban. I was very sorry for that.

“I’m just very sorry for the day the team had in general. I wish I could have seen Esteban there or something would happen differently.

“A tough day for us, but this is racing.”

Ocon and Perez have a history of collisions and spats having done so in Baku and Belgium last season.

Eventually, Force India had no choice but to introduce team orders in a bid to secure fourth in the Constructors' Championship but had been free to race this year and had done so without incident until Sunday.

“We’re back to the old rules,” the American team boss declared.

“The team is more important than one individual. If that’s what they’re going to do, we’ll have to take control from here.

“We allowed them to race on Lap 1 whereas in the past we didn’t let them race on Lap 1 and now we can remove that.”

For Perez, it was an eventful race throughout as a decision to be among the earliest drivers to pit left him stuck behind the Williams of Sergey Sirotkin.

Frustrated, the 28-year-old would produce an erratic move as he duelled with the Russian through the grandstand section, driving into the side of his car and picking up a drive-through penalty.

That would take him out of any contention for points, rounding off a disastrous day for Force India.