Kane, who has scored 188 goals in 288 appearances for Spurs, was tentatively linked with a move to Man United earlier in the summer.
Those links have stopped gathering pace for the time being, however, with the Red Devils currently working on deals for Jadon Sancho and Sergio Reguilon.
Merson says Manchester United are ‘crying out’ for a new striker and should be looking to secure a stunning deal for Kane.
He told Sky Sports: ‘I’m probably Harry Kane’s biggest fan after his Mum and Dad! I look at him and I think: “What are you going to win at Tottenham?”
‘He’s one of the best in the business at scoring goals, but he’s scoring 30 goals a season and not getting chances to win trophies, what’s the point in being there?
‘I just cannot believe nobody has come in for him. What am I missing?!
‘Manchester United are crying out for a goal scoring centre-forward, and if I’m being honest I think Man City are too.
‘If Sergio Aguero gets injured, they miss too many chances. Aguero is two shots, one goal.
‘I just don’t understand why there isn’t more talk about a team signing Kane.’
Despite developing into one of the most prolific strikers in the world, Kane is yet to win any silverware and was unable to prevent Jose Mourinho’s side from suffering a 1-0 defeat to Everton on Sunday.
‘That’s it. It’s massive. I said on air with Sky last year – and I got crucified for it – this is the way Mourinho plays.
‘You’re not turning up at Spurs this season seeing 5-4s. It’s all well and good talking about the fitness, but it’s also the way he plays.
‘He’ll sit deep, and he’ll counter-attack teams. It’s OK when there’s nobody in the ground, but with 60,000 people at Spurs, and they’re seeing that, they’re not going to be happy.
‘They’ve seen some entertaining football there over the last few years. Over the last few years they’ve been as good as anybody, before the Champions League final.
‘I can understand if he plays that way against Man City, but it’s Everton, at home! If you’re a Spurs fan watching that, you’re thinking: “Where are we going?”
‘I know there’s a long way to go, but you might be the most loyal Spurs fans in the world, you cannot sit there and honestly think, hand on heart, that you’re going to finish in the top four this season.
‘It’s a shame for them, considering where they’ve been in the last few years.’