HUNGARIAN Olympic champion and multiple world record holder Katinka Hosszu announced on Thursday night she had split with her US coach and husband Shane Tusup, who then levelled stunning cheating allegations against her.

Hosszu cited ‘personal issues’ for the breakup, but Tusup claimed the pair parted ways after she slept with her training partner, Daniel Dudas.

“You deserve to know the truth, those ‘personal issues’ were that she betrayed me,” Tusup, 30, said in a written statement.

Hungary's Katinka Hosszu celebrates with her husband Shane Tusup after winning the women's 200m Individual Medley final at the 2017 FINA World Championships. Source: AFP

“Her confession to me, she destroyed the sanctity of our marriage by stepping out of the marriage, by sleeping with her training partner, Daniel Dudas.

“At the end of November, I was completely blindsided by the sudden overnight strain on our marriage, and any hope to reconcile the marriage was completely sabotaged by Katinka continuously misleading me into believing the issues were all me and my character.”

Tusup wrote that he tried to forgive her after her alleged confession, but claimed there was ‘no real effort on her part’ to mend the relationship.

He added: “I truly believe she never loved me, but simply loved the way I was devoted to her.”

Tusup claimed in a written statement the pair parted ways after Hosszu slept with her training partner, Daniel Dudas. Source: Twitter

Hosszu, 29, announced the personal and professional split in a Facebook post that seemingly foreshadowed the imminent allegations.

“I would like to get ahead of the gossips, sadly Shane and I haven’t been able to resolve our personal issues, therefore we are no longer working together,” she wrote.

“I am still preparing for the upcoming competitions while looking at my options for my support team.”

Last December, Hosszu said that their relationship was “undergoing trials,” and attended separately a Hungarian sports gala where Tusup pledged that he “would work to change”.

Hosszu with her trophy for best female swimmer of the meet at the FINA World Swimming Championships. Source: AFP

Nicknamed the “Iron Lady” and currently Hungary’s most successful sports star, Hosszu met Tusup when both were swimming at the University of Southern California.

The American took over as her coach soon after a disastrous London Olympic Games in which she missed out on podium finishes despite high expectations.

With Tusup as her coach, Hosszu became one of the world’s top swimmers, winning three golds and a silver at the Rio Games.

Tusup’s intensive training methods for Hosszu raised eyebrows among some swimming insiders. Source: News Corp Australia

She also won two golds each at World Championships in 2013, 2015, and 2017.

Her next major target is the 2020 Olympic Games in Tokyo, she told Hungarian media earlier this year.

Tusup’s intensive training methods for Hosszu raised eyebrows among some swimming insiders, but his emotional reactions to her races also won admirers.

NBC’s official Olympics Twitter account in 2016 urged women to “find someone who loves you the way Katinka Hosszu’s husband loves her”.