Evan Ferguson's late leveller earned the Seagulls a deserved point in their 2-2 Premier League draw at the King Power Stadium.
The Foxes rallied after Kaoru Mitoma's brilliant opener as Marc Albrighton and Harvey Barnes put them 2-1 up.
But De Zerbi felt the visitors should have had a penalty after Luke Thomas tripped Danny Welbeck in the second half before Barnes struck.
The manager - who was booked on the touchline - was upset after referee Bramall failed to award the Seagulls a spot-kick and felt the official made a mistake.
"Today was a bad day for the referee, a very bad day," he said, as the Seagulls climbed to sixth in the Premier League table.
"I don't like to speak about referees so much or to cry about the referee after the game. I hate (it), I don't like the people who cry about the referee but today it is clearly a penalty.
"I'm not able to understand what the referee was watching. If you want you can help me because I don't understand. There is VAR but I don't know if it was working or not.
"It's an important point. I know football and I know sometimes you can lose this game and I think we deserved to win.
"We played better than Leicester in the second half. There was only one team on the pitch, but we could lose the game because we made some mistakes.
"I'm happy for the performance of the players, I'm proud of the way we played after Leicester's second goal."
Jan Paul Van Hecke headed the ball over before Mitoma created a brilliant opener after 27 minutes.
Brighton sliced through the Foxes midfield with ease and Pervis Estupinan found Mitoma on the left.
The Japan international was given far too much space by Timothy Castagne and he cut inside to find the top corner from 20 yards.
Brighton were comfortable but their lead lasted just nine minutes when Albrighton fired in at the far post after Barnes and Youri Tielemans had been denied.
De Zerbi wanted the penalty early in the second half and was booked for his protests. Solly March then blazed over from 12 yards and it was a costly miss as Leicester grabbed the lead when Barnes hooked in at the far post after Thomas touched on Albrighton's corner.
Brighton were smarting - having been so dominant - and Ward denied March and Alexis Mac Allister before Ferguson levelled with two minutes left when he guided in a fine header from Estupinan's cross.
"We should have won the game but it (coming from behind) is important," said Foxes boss Brendan Rodgers. "Now moving into the second half of the season every point counts.
"I'm disappointed with the first goal because we gave the ball away cheaply. It's a quality we lack, but he scores a great goal.
"At this level you have to have a pride with the ball. Not enough of our players care enough when they have it. You have to deal with the ball at the highest level.
"Then it's about a response, we spoke about it, that if we went behind it was a chance to show our spirit.
"The players fought right to the end. They were probably out on their feet a little bit. Overall the spirit was there and we had some of our players back."