Horner said the Spaniard had drifted across the track towards Perez to cause the collision that wrecked the Mexican's race and robbed Red Bull of valuable constructors' championship points.
"It looked to me, just looking at the replay, like Carlos drifts across the circuit to the left-hand side," said Horner.
"It's done a huge amount of damage -- a massive accident.
"So, it cost us points, crucial points, for Checo and for the constructors. So very disappointing."
The pair tangled while battling for third place behind winner Oscar Piastri of McLaren and Ferrari's Charles Leclerc.
"He deserved a lot more," said Horner of Perez who seemed to have recovered his form after a long run in the doldrums during which he scored only 36 points in 10 races as Red Bull lost their dominant position.
Piastri's victory along with team-mate Lando Norris finishing fourth lifted McLaren 20 points clear of Red Bull at the top of the teams' championship, ending the champions run of 55 races as leaders.
"He should at the very least have been on the podium today," added Horner, who suggested a penalty should be in store for Sainz at next weekend’s Singapore Grand Prix.
Sainz and Perez had both declared their own innocence over the shunt and after a stewards' hearing both driuvers escaped without penalties.
In a statement, the stewards said they deemed "this to be a racing incident with neither driver being predominantly at fault" and said they would take no further action.
The stewards reviewed the incident and studied the driving lines of the drivers on previous laps, noting that Sainz was "on or close to his normal racing line".
They added that there was nothing unusual about Perez's racing line, but said 2he could have done more to avoid the car that he had a better view of".
"I honestly don’t understand what happened," said Sainz.
"I am 100 per cent convinced I did nothing wrong and did nothing over-aggressive."
Perez said: "Honestly, it is such a shame. It's a disaster for the championship and not the way to end a weekend."
Max Verstappen, who finished fifth, also escaped punishment from the stewards for overtaking cars under the Virtual Safety Car conditions deployed for the final lap after the Sainz-Perez crash.
He was given a formal warning along with Haas's Nico Hulkenberg and Alpine duo Pierre Gasly and Esteban Ocon.
