Oscar Piastri was left frustrated by Carlos Sainz's "unacceptable" lack of awareness that cost him a chance to challenge for the Hungarian Grand Prix victory.

Piastri made a strong start to the race at Hungaroring, leading the opening stint after overtaking team-mate and pole sitter Lando Norris.

However, he later made contact with Sainz on Turn 2 while trying to lap the Spaniard, who was battling Fernando Alonso for 16th at the time. Sainz later received a five-second time penalty for causing the collision.

Piastri lost control of his car, allowing Norris, who went on to claim his first win of the season, to emerge from the pits ahead of the Australian.

Piastri ultimately retired with 15 laps remaining due to gearbox problems but remained unimpressed by Sainz's failure to see the blue flags that indicated he was about to be lapped.

"I knew there were blue flags, but there were blue flags on all the marshal signals; I was right behind him for a sector," Piastri explained.

"I couldn't believe what happened. Getting crashed into by a lapped car is never one of the things you expect that can go wrong in your race, and today it was, so I don't really care if he didn't see me.

"The fact that he didn't, and no one told him, or there was a lack of complete awareness, is unacceptable."

On the rest of the race, Piastri added: "[Overtaking Norris] was definitely the highlight of my race, and it went pretty downhill from there.

"A lot of things to unpack. Firstly, the pace on the hard tyres was nowhere, and then obviously getting taken out by a backmarker is never really one of the things you think can go wrong. But I was proven wrong. Then obviously the gearbox, so not the easiest of days."

While Piastri endured a disappointing race, drivers' championship leader Kimi Antonelli recovered to finish third.

Antonelli had qualified in fourth but was demoted three spots after he failed to slow sufficiently under the yellow flags caused by a Max Verstappen spin in the third qualifying session.

He clinched a podium spot from seventh on the grid, ensuring he heads into the summer break with a 50-point lead over Lewis Hamilton at the top of the standings.

"It was a tough race," Antonelli said. "It was really hard to overtake, so we had to do something with strategy.

"Of course, I'm very happy [with the title lead], and it's the best way to go into the summer break.

"I think [the race] was big damage limitation, and we've got to keep pushing because the second half is going to be hard, but we'll try our best."