* Leadbetter says decision came from Ko
* Ko out of winner's circle since July
* Slump could be attributed to burnout (Adds fresh quotes, details)
Dec 7 (Reuters) - World number one Lydia Ko, who clinched the most recent of her 14 LPGA titles in July before enduring the first barren spell of her young but already stellar career, has split from her coach David Leadbetter after three years working together.
Ko and Leadbetter joined forces shortly after she turned professional in late 2013, with the then 16-year-old leaving her New Zealand-based coach Guy Wilson after 11 years in tandem.
Leadbetter, who announced the split on his website, later told New Zealand media the decision had been a "surprise" but it had come from Ko and he felt her family had been a major factor in the thinking.
"We have had a pretty good relationship but it is not easy coaching three people at once," Leadbetter told New Zealand's Radio Sport, while adding he felt the 19-year-old was under immense pressure.
"Lydia is not a machine and she can't play well week in week out. She's not going to win every week. All of these top players ... have their ups and downs and there are times when golf is not going to be plain sailing.
"It has been a little bit difficult over the last few months when she hasn't been playing well. Her father has got a bit more involved and is trying to throw some swing technique at her.
"It's just in the decision making. Her parents are lovely people but I think they are little naive."
Ko's decision to leave Leadbetter came just two months after she fired her former caddie Jason Hamilton, something Leadbetter said had been a mistake.
"Changing her caddy was a crazy decision ... we weren't in favour of that," Leadbetter added.
The 19-year-old, who has won two major titles, has not tasted victory since the Marathon Classic in July and has finished outside the top 40 in three of her last six LPGA starts.
Ko ended the 2016 LPGA season in second place behind Ariya Jutanugarn in both the official money list and the Race to the CME Globe, and was also pipped by the Thai in the hunt for Player of the Year honours.
"She has had a very poor last few months," Leadbetter added. "There are a lot of factors. She's changing her equipment. She has had a lot on her mind. She has a lot more sponsor and media commitments as world number one.
"She has lost a lot of her fitness level. After the Olympics, which she put so much energy into, she was absolutely spent.
"Now she looks completely burnt out." (Reporting by Mark Lamport-Stokes in St. Augustine, Florida; Editing by Greg Stutchbury/Amlan Chakraborty)