Former world number two Alexander Zverev will not face disciplinary action following an investigation into allegations of domestic abuse.

In 2020 she accused Zverev, 25, of violence and emotional abuse during their relationship, which he denies.

The ATP decision could be "re-evaluated should new evidence come to light".

The governing body of men's professional tennis said it commissioned a private investigation company, the Lake Forest Group, to look into the allegations.

It conducted "extensive interviews with both Sharypova and Zverev" and spoke to 24 other people, including family, friends and players.

The 15-month investigation reviewed text messages, audio files and photos, including material "voluntarily extracted from Zverev's electronic devices via a third-party forensic expert".

"Based on a lack of reliable evidence and eyewitness reports, in addition to conflicting statements by Sharypova, Zverev and other interviewees, the investigation was unable to substantiate the allegations of abuse," the ATP said.

Zverev, a two-time winner of the season-ending Tour Finals, reached a career-high ranking of number two last June before suffering a serious ankle injury during a match against Rafael Nadal at the French Open. He returned to action this month.

In 2021 Zverev took legal action against Sharypova and an online publisher after she made further allegations of abuse. He also backed calls for the ATP to introduce a domestic violence policy.

ATP chief executive officer Massimo Calvelli said the situation had "shown the need for us to be more responsive on safeguarding matters".

"The seriousness and complexity of these allegations required an extremely thorough investigative process and considerable resources," he said.

"It also required us to turn to specialist investigators, which was new ground for ATP."

The ATP commissioned a separate independent safeguarding report in 2021.