The Magpies suffered their heaviest defeat of the campaign and their biggest loss at St. James' Park since 1925.
"Firstly, for the squad and the staff, we apologise for that performance," Pardew told nufcTV.
"We know in the next three games we've got to get at least one win, if not more, and that needs to start at West Ham.
"I'm afraid today was a real low point in my career here because that performance, as the scoreline suggested, just was not good enough.
"I thought in hindsight the team selection didn't work for us. The performances looked affected by the goals; to be 2-0 down so early looked like it affected a few bodies.
"All my teams are organised and are on the front foot, looking to win the game, but that wasn't the case today.
"We looked disorganised and it's not anyone's individual problem - it's a collective problem we've got to put right.
"We've got three or four people in that dressing room who have been in this position and got relegated and we're going to have to draw on that experience to make sure it doesn't happen again."