Lydia Ko must "leave the nest" and take control of her own career if she is to return to the top of women's golf, says her former coach David Leadbetter.

The 22-year-old Kiwi is in the worst slump of her professional career and currently sits at 23rd in the world golf rankings after holding the number one spot for 84 weeks during her peak.

Her nightmare form continued last week at the British Open, where she shot a horror 80 in the second round – following up a four-over 76 on the first day – to finish the major in second last, missing the cut by 10 shots.

It was her second consecutive missed cut at a major after having similar struggles at the Evian Championship in France where she finished seven shots behind the cut line.

Leadbetter, who oversaw Ko's rapid rise where she won 17 LPGA titles and two majors, says it's been tough to see the downfall of one of golf's brightest talents and points to her parents' involvement in her career as the main reason for Ko's decline.

"It really is a very sad situation to observe," Leadbetter told Radio Sport. "Her team have to be thinking that they have made some huge mistakes taking an unbelievably talented player and turning her into ordinary.

"I hope she gets it back but restoring confidence is never the easiest thing to do. Her parents have a lot to answer for – a case of unbelievable ignorance.

"I'm angry, I'm sad because to me I know what she's capable of doing. And to see her play like this, it's just very sad to see."

Leadbetter has long been critical of the role that Ko's parents, Gil Hong and Tiny Hon, have played in their daughter's career.

"They tell her when to go to bed, what to eat, what to wear, when to practice and what to practice. And they expect her to win every tournament," Leadbetter once said.

Since parting ways with Leadbetter in 2016, Ko has gone through several changes from coaching personnel to equipment tweaks, none of which have seemed to work when it came to improving her game – the changes only seemingly making things a lot worse.

Leadbetter says it's been one change too many.

"At the end of this year it'll be three years since we worked together. She had a phenomenal start to her career, probably a greater start to for me than Tiger Woods when you look at it from the number of tours she's played and her win ratio and major win ratio.

"The problem is when you start changing everything. As many changes as she's made, not only coaching, caddies and equipment, and sports psychologists and trainers, she's also changed her body type now.

"I think there's a lot of factors here. Who knows what's going on inside her head right now and obviously her team needs [to get] things together there because the longer it goes on, the tougher it is for her to get out of it."

Leadbetter, who was Ko's swing coach from 2013 until the end of 2016, said he would be open to returning to his former role if her parents were to take a step back.

"I like Lydia. She's a tremendous person, she's a tremendous ambassador for the game, she's a tremendous ambassador for New Zealand golf. It (returning as Ko's coach) would only be down to one provider and that to me would be where she was just in full control of what she was doing.

"I just think that those parental issues have been such that I think she's been misguided. I think her parents are naive as far as what should happen in the game of golf.

"I think her parents need to sort of let her go and do her thing. She's 21-22 years of age now. She could control her own career. She should know what's best for her.

"She's not a 12-year-old anymore. So they need to let her go, let her fly, let her leave the nest so to speak and find her own way. If she can do that, I mean yeah we could see Lydia back."

For now, Leadbetter has one piece of advice for Ko.

"My advice would be look to take a break right now. She doesn't need to play for the rest of the year. Just get her head together, relax, get away from the game and rethink this whole thing. There's probably a lot of factors going on here.

"Sometimes you've got to take a complete break from the game, get your mind rested, get your body rested and then [come back] and play next year."

Lydia Ko's coaches since going pro

• David Leadbetter – Ko's swing coach from 2013 until the end of 2016.

• Gary Gilchrist – in early 2017, out early 2018.

• Ted Oh – in early 2018, our April this year.

• David Whelan – Ko's current swing coach who took over from Oh. He's best known for the Korda sisters, Nelly and Jessica, who both rank in the top 15 in the world