Harper told the Evening Chronicle that Pardew was far from happy with his team's last performance against Reading, which ended in a 2-2 draw.
The Magpies face a testing week, where they host unbeaten Bordeaux in the Europa League before taking on Manchester United in the Premier League this weekend.
Harper said: "The manager wasn't happy with the performance. At half-time we knew if we improved we could have gone on to win the game. It was a disappointing performance, but our overall battling spirit saw us through.
"Obviously, the manager's made it very, very clear that it needs to improve, and very quickly. The gaffer wants us to come out of the traps quickly.
"We've got two huge games on Thursday and Sunday, and he expects to see a response against a Bordeaux team which got a fantastic result in the Europa League and Manchester United at St James' Park needs no build-up whatsoever."
Harper is currently enjoying a spell in the Newcastle first team, with first-choice keeper Tim Krul out with an elbow injury picked up on international duty.