A first-half double from Graziano Pelle and further strikes from Jack Cork and Morgan Schneiderlin were the difference as Newcastle produced a lifeless display at St Mary's Stadium.
The result leaves Newcastle bottom of the Premier League table with two points from four games, heaping the pressure on Pardew, who was reported to be a heavy defeat away from losing his job heading into the game.
But in spite of the mounting speculation over his position at the club, the former Southampton and West Ham boss, who refused to turn up at the post-match press conference, is remaining defiant.
He told BBC Radio 5 live: "Until told otherwise, I will continue to prepare the team for next weekend."
Turning his thoughts to matters on the pitch, Pardew earmarked individual errors as the primary reason for the drubbing, although he believes criticism directed at him from the fans may have affected his players' confidence.
"They [criticisms] are fair because you can't get beat 4-0 as Newcastle manager - I've had it a few times at this club - it's tough to take," he said.
"It's not easy to digest and not easy for the players to play under those circumstances.
"We have to be strong and tough it out this week and try and come back next week."
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