Maddison went down in the box under a slight challenge from Jamaal Lascelles – Alan Shearer suggested it a “dive” on Twitter – and Youri Tielemens converted it.
Howe felt the decision should have gone to VAR. United’s head coach said: “I’m surprised that it hasn’t gone to VAR for the referee to have another look himself. It’s obviously a contentious decision, and I’d always encourage the referees to go and have another look themselves.
“I don’t think the scoreline is reflective of the game, and I think the penalty decision has obviously had a huge bearing on the outcome. In my opinion, I don’t think it was a penalty.
“Maddison is going over before the contact is made, and it’s just disappointing the referee didn’t go over to have another look at it himself. That would have been the best decision.”
Leicester manager Brendan Rodgers said: “We set the trap, pressed the game – and the referee calls it well, for me. That's a reward for being brave and having courage to press the game. I felt there was contact, and there is contact.”
Newcastle’s performance unravalled after the break, but Howe didn’t feel that the final scoreline reflected the game.
"It was a strange game, because I thought we were OK for large parts,” said Howe. “We were OK in the first half, and were a threat at times. We conceded a goal with the penalty, which was debatable whether it was.
"The scoreline looks like a heavy defeat, but I didn't think it felt like that at all.”
The game had seemingly been an opportunity for Newcastle given that Leicester, jaded from a Europa League tie on Thursday night, were missing a number of players.
“If we'd have shown more composure in the attacking third, we could have made more of the moments,” said Howe. “We just let the game slip away from us.”
Newcastle remain 19th in the Premier League with 10 points from 16 games ahead of the December 16 game against second-placed Liverpool at Anfield.
1. Phillips details revealed
West Ham keen on Liverpool defender Nat Phillips but the Reds will only let him go on a permanent transfer for a fee of £10m. Burnley and Bright have also been linked. (Various) (Photo by Marco Luzzani/Getty Images) Photo: Marco Luzzani
2. Brighton set to recall Walton
Ipswich Town loanee Christian Walton is set to be recalled by Brighton so that the Seagulls can sell him to a Championship club in January. (The Sun) (Photo by Nathan Stirk/Getty Images) Photo: Nathan Stirk
3. Toffees keen on Winks
Everton have continued to keep tabs on Tottenham Hotspur midfielder Harry Winks. (Sunday People) (Photo by Martin Rose/Getty Images) Photo: Martin Rose
4. West Ham lead Johnstone race
West Ham have emerged as clear favourites to sign West Brom goalkeeper Sam Johnstone ahead of Southampton and Spurs. (The Sun) (Photo by Justin Setterfield/Getty Images) Photo: Justin Setterfield