The Villans were on course for a third successive win when Christian Benteke's crisp finish put them ahead, only for Liverpool to strike twice in the second half.
Jordan Henderson levelled just two minutes into the second half after a sharp counter-attack and Steven Gerrard scored what turned out to be the match-winner from the penalty spot after a reckless foul from Nathan Baker on Luis Suarez.
Villa remain in the relegation places on goal-difference with seven games remaining, however Lambert did not think there was much between the teams.
He told Sky Sports: "I thought first half we were excellent - I really did. There was Gabby's chance which if he miskicks it probably goes in but the keeper (Pepe Reina) did well and stood up to it. There wasn't much in it in the second half but we never had the fluency which we did have in the first half, but you can't give away goals like we did. It was a definite penalty, I've just seen it."
Asked how disappointed he was to concede so soon after half-time, Lambert added: "It was a poor goal two minutes in, when we were attacking, but Liverpool can do that with the players that they've got. You've always got to be switched on against them but from our point of view it's a poor goal."
Next up for Villa is an away trip to Stoke City and Lambert insists confidence remains high going into the business end of the season.
He said: "It's a collective thing. Everyone is in it together and we move along to the next game. We are certainly playing well enough to win games.
"We're certainly playing well enough and we don't look like a team who are down the bottom at the minute. If we keep going we'll win more games than not.
"Confidence is a big part of the game. We are not lacking in that. We are making errors because we're young but the confidence is there."