Newcastle are only two points above the relegation zone and Pardew warned the club must act if they are to remain in the top flight.
"We need to make sure we are a Premier League team next season. Our team today is a shadow of the team we can put out," he said. "We know we need to get some bigger players who can handle the situation of carrying a Newcastle jersey, whether that's a signing or getting a player back from injury.
"It's important to spend during this month. I'd like to see another player come in through the door to join Mathieu Debuchy in the next week or so. It's difficult to get transfers in this window but we'll have to do everything possible.
"As Newcastle manager coming to Brighton in the third round of the FA Cup I'm aggrieved that I couldn't put out a stronger team than that.
"There are young players who have given everything there, their maximum performance. But unfortunately they shouldn't be playing for Newcastle in the third round, they should be in our development team.
"We're not too big to go down and we accept that."