England manager Roy Hodgson announced his squad for the upcoming games against Slovenia and Scotland on Thursday, but opted against selecting the 25-year-old forward, who has scored five goals in nine Premier League games this season following the club's promotion from the Championship in May.
Hodgson has instead picked Saido Berahino, Danny Welbeck, Wayne Rooney and Rickie Lambert as his attacking options.
However, Redknapp thinks Austin - playing for non-league Poole Town just over five years ago - deserves a first call-up if he continues to come of age in the top flight.
"Charlie's improving and if he keeps scoring goals there no reason why he can't in the future," said Redknapp.
"He's a great lad, good attitude, not a minute's problem and he enjoys being a footballer. He's had it the hard way and I think he realises just how fortunate he is to be doing what he does.
"If he keeps scoring goals and improving his game there’s no reason he can't make the breakthrough."
Former Burnley and Swindon Town striker Austin has enjoyed a meteoric rise to the Premier League having juggled a career as a builder with his football commitments earlier in his career, but Redknapp believes his feet are planted firmly on the ground.
Speaking ahead of QPR's league clash with defending champions Manchester City this weekend, Redknapp said: "He appreciates being a Premier League player.
"He thinks back probably to when he was up at five or six [in the morning] laying bricks through the winter - on a building site or whatever.
"This is fantastic for him, maybe we should put a few more on the building sites in the morning. I don't think it would do them any harm."
