Toro Rosso's Tost dismayed by Perez Monaco GP move on Kvyat

Running on fresh ultra-soft tyres, Perez attempted to pass Kvyat at Rascasse for ninth place with six laps to go, but the duo made contact.

Kvyat retired after the impact, calling it "completely desperate", while Perez continued and ultimately finished 13th.

Stewards investigated the incident and handed Perez a time penalty, which didn't affect his position, and penalty points on the Force India driver's licence.

Tost was dismayed with Perez's approach as the incident robbed Toro Rosso of a double-points finish, with Carlos Sainz Jr finishing sixth.

"It was Checo's fault," Tost told Autosport. "You don't just drive in there like that.

"Just look at what is destroyed - the middle of the sidepod [on Kvyat's car], the left-front wheel [on Perez's].

"You do not need to discuss the fault - it's 100% Checo's fault. You don't do this.

"Until this incident, we were with both cars in the points.

"All weekend, we had a very competitive car and Carlos showed a fantastic race, defending his sixth position, bringing it home.

"Daniil was there, too, but Perez took him out of the race."

Sainz told reporters that he felt Toro Rosso had the fourth or fifth best car in Monaco.

Tost believes the STR12's form "depends on the race tracks", but he was pleased his team is currently meeting its target of fifth in the constructors' championship.

"It will be difficult for us in Canada and Azerbaijan but our engineers are working hard to find a set-up to get us in the points in these races," he said.

"[Engine supplier] Renault is always coming with some small developments, so we will see.

"We're fifth in the constructors' championship, nine points ahead of Williams.

"We need to keep fighting for this position, this is our target."