Ashley has always been a controversial figure on Tyneside ever since he paid £135million to take over the club in 2007. He was initially hailed for saving Newcastle from their financial woes, but he soon found himself a pariah figure for the way he handled the exit of hugely popular manager Kevin Keegan.
His two unsuccessful attempts to sell the club did him no favours and the £35million sale of Andy Carroll to Liverpool, and the subsequent departure of other key players, made Ashley even more of a hate figure at the club.
He has, however, found a sympathiser in Redknapp, who ahead of Sunday's game against the Magpies praised the Newcastle owner for investing money into the club, and for the appointment of manager Alan Pardew, who has led the club to fourth in the table thanks to a seven-match unbeaten run so far this season.
"To be honest the chairman has had some grief up there and he's put millions and millions of pounds in to the club," said Redknapp, who turned down the Newcastle manager's job a year before Ashley bought the club.
"Alan Pardew has done a great job as manager. They look a strong outfit at the moment.
"(Pardew's predecessor) Chris (Hughton) went up there and did well, got them promoted. Obviously Mike Ashley wanted a change and Alan has gone there and done a great job.
"The chairman's spent fortunes up there and they're still shouting and moaning. He's spent about £100million and they're still calling him names."
Redknapp takes his team to St. James' Park on the back of a four-match winning streak that has dragged the club from the bottom of the table to sixth, with a game in hand on their rivals.
Key to the club's revival has been the form of the Spurs defence, and in particular that of fit-again captain Ledley King. King missed most of last season with a serious groin injury and he was also troubled by the chronic knee problems that have dogged him throughout his career.
Redknapp has hailed the defender's influence on the side and hopes that he will remain injury-free for the rest of the campaign.
The Spurs boss said: "Ledley defies all belief. He comes in and goes in the medical room, does a bit on the bike or something and that's it, he doesn't come out and play football with the rest of the lads in training because it takes four or five days for his knee to go down because it swells up so bad.
"He can just come out and play on a weekend. It's crazy in today's Premier League. I'm just hoping he'll be fit to play because he's just an amazing player.
"He gives you an air of confidence knowing he's there and that's how I feel when he plays. He's like Alan Hansen was when he played for Liverpool.
"Younes Kaboul had a disastrous two games at the start of the season, but since he's been playing alongside Ledley it just seems that Ledley has sorted him out."
King's lack of training has cost him what Redknapp thinks could have been a stellar international career. King has only played 19 times for England throughout his career and, though he was named in Fabio Capello's 2010 World Cup squad, he did not play after suffering a groin injury while in South Africa.
Redknapp, who is favourite to take over from Capello next summer, rates King as one of the best centre-halves in England but thinks the 31-year-old is unlikely to play for the Three Lions again.
"He's as good as any defender in the country. He's a smashing boy as well ," Redknapp said.
"(But) I think that (his international career) would be gone. They took that risk last year and it didn't work out for them."