Harry Kane's future at Tottenham is shrouded in doubt and former England striker Alan Shearer believes it is now or never if he does want to leave.

Kane has never been shy about expressing his desire to win trophies at Tottenham, calling that the "next step" when the club moved to their new stadium from White Hart Lane.

Spurs flirted with that possibility under Mauricio Pochettino, finishing second in the 2016-17 Premier League season and reaching the final of the Champions League two years later.

But under Jose Mourinho they are going backwards, with Spurs seventh in the league and six points adrift of fourth-placed West Ham, meaning Champions League qualification may elude them.

Kane has proven himself as one of Premier League's all-time greatest strikers, with his haul of 162 goals bettered by only seven players, while his 121.8 minutes per goal is the third best among those to have netted at least 100 times.

But recent media speculation has suggested Kane is losing patience, and Shearer – who famously joined Newcastle United over Manchester United in search of trophies and failed to win any – thinks he may not get another opportunity to take his career to the next level.

Writing in his column for The Athletic, Shearer said: "I've got way too much respect for Harry as a player and a man to offer him advice on a decision that I know for myself is rarely linear and that may not, in the end, be his to make. What I would say, though, is this: if he's going to leave, it looks like this summer or not at all.

"Harry is 28 in three months and this is why I think we're approaching a pivotal moment. He's at his peak, the ready-made article, an absolute guarantee of goals wherever he plays and the opposite of a gamble, but a buying club is going to want three or four of his best years in return for what would certainly be an exorbitant transfer fee. This is that time. Twelve months down the line and it becomes that bit more difficult to justify.

"The one indisputable fact is that Harry is under contract at Tottenham for three more years. That six-year deal he signed in June 2018 was a fantastic piece of business by Daniel Levy and his club.

"It tied down their most saleable asset and it gives them a thick layer of protection now. I'm not convinced it was quite so great for Harry, even though the landscape at Spurs was much more positive back then.

"The point is that Harry could no longer say the same things about winning the Premier League [as he did in 2018]. Would the picture change at Spurs if Mourinho went? Maybe.

"As Leicester City and West Ham show, a place in the top four is open to clubs that get things right, but in terms of more than that? Spurs look a long way off. And so that leads back to the same question: is it enough?"

Shearer routinely insists he has no regrets over choosing to join Newcastle instead of going to Old Trafford 1996, despite the Red Devils going on to win the Premier League title in four of the following five years, including their historic 1999 treble that included Champions League success.

For his part, Shearer went on to become Newcastle and the Premier League's record goalscorer, feats he treasures, and Kane appears on course to accomplish similar achievements with Spurs.

But if it is trophies rather than personal accolades that Kane thirsts for, Shearer can see only one option – not that there is ever a guarantee of success, regardless of whether he ends up at United, Manchester City, Real Madrid or Barcelona.

"When I moved to Newcastle for a world-record fee in 1996, I did so with the aim of winning trophies. That was the driver for me, as well as the pull of coming home," he continued.

"It didn't work out like that, of course, but for most of my decade at St James' Park and with lots of ups and downs on the way, we were trying.

"Harry is a big player; he won't accept staying at Spurs for the sake of it. He has to have something to buy into. Right now, winning means leaving.

"None of that means Harry should leave; to repeat, that's not something I would ever say, but if we judge him on his words from two or three years ago, then it's certainly a subject he will be considering now.

"If it ends with no trophies, does that mean hell have had a s*** career? No, of course not. All that said, the great players do not settle. They always want more and they push for it. And Harry is a great player, which is why it feels like he and Spurs are approaching a moment of definition."