Middlesbrough head coach Aitor Karanka acknowledged his side had been beaten by “the best side in the league”.
But he felt the first goal which sent Leicester on the way to victory should have been disallowed.
Karanka said: “Before the game I said Leicester were the best team in the league. I still say that now; but they did not need any extra help from the referee.
“But we need to learn that if you concede the first goal or make a mistake you have to keep working in the same way throughout the game.”
This was the Foxes’ seventh win in a row and took them eight points clear at the top of the Championship.
After a forgettable first half when both sides struggled in difficult conditions following a torrential thunderstorm, the Foxes took control.
“We did well in the first half and had chances to score, but in the second half they were more intelligent than us,” continued Karanka. “They took advantage of the referee’s decision and raised their game while we went down.
“We could have been better in the second half. The game is not over because you concede the first goal. We felt the ball had gone out of play in the build-up to the first goal but that is no excuse.”
Middlesbrough were undone by the pace of Jamie Vardy up front and he put Leicester ahead with his 10th goal of the season in the 52nd minute.
Boro protested furiously, but in vain, and Vardy was in the thick of things again in the 71st minute, racing into the penalty area before being brought down by Rhys Williams.
Shay Given saved David Nugent’s spot kick, his 12th penalty of the season, nine of which have been successful. Two minutes later however, Williams flattened Vardy again, and from Matty James’s free-kick, Ritchie De Laet scored with a far post header.
Leicester City: Schmeichel, De Laet, Morgan, Moore (Wasilewski 9), Konchesky, Knockaert, Drinkwater, James, Dyer (Mahrez 79), Nugent, Vardy (Phillips 79). Unused substitutes: Hammond, King, Taylor-Fletcher, Logan.
Middlesbrough: Given, Varga, Ayala, Williams, Friend, Whitehead, Leadbitter,Adomah,Ledesma (Chalobah 77),Carayol, Jutkiewicz (Kamara 59). Unused substitutes: Butterfield, Emnes, Konstantopoulos, Gibson, Omeruo.
Referee: S Martin (Staffordshire).
Man of the match: Shay Given.