Gareth Bale was sold by Spurs last season for £80m to Real Madrid, and the club reinvested the cash in deals for Erik Lamela, Roberto Soldado and Christian Eriksen, with only the Denmark international proving to be a hit in the Premier League so far.
Redknapp feels that the club's approach towards team building needs to be altered if they are to become a top-four side.
He told Sky Sports News: "A few seasons ago Tottenham had closed the gap on Arsenal – but now they're further away than they have been in a long time.
"Spurs are miles away from being a top four team now and that's down to their transfer policy. The club haven't spent their money with a great thought process.
"The director of football, Franco Baldini, has brought a lot of players in but you can't just throw them together and expect it to work, you need a system. Spurs need to re-think their structure and how they sign players."
Spurs face Arsenal in the North London derby later today at the Emirates Stadium.