The Magpies suffered a fifth-straight defeat in the Premier League on Saturday afternoon, falling to a 2-1 loss against Swansea City at St James' Park.
"Everyone is very disappointed, of course," Debuchy told the club's official website following the game. "We wanted to go out there and get a win, so to lose - and in that manner, with a last-minute penalty - was really disappointing. It is always harder to take like that.
"I think we deserved at least a draw from that but we have to look back at the mistakes we made. We lost from two set pieces - a corner and a penalty - and that is nowhere near good enough.
"I have never known five defeats in a row. It is something which is not acceptable for a club like Newcastle United and a squad like ours. It is something we simply should not be doing."
Alan Pardew's side return to action a week on Monday when they take on Arsenal at the Emirates Stadium.