The Iron Man star was called to the stand in a Los Angeles court on Friday (14Aug15) as part of his bid to have the former couple's costly 2012 divorce settlement dismissed, insisting he signed it under duress.

During his testimony, Howard broke down in tears as he detailed the alleged blackmail plot his ex reportedly devised to win a bigger pay out, claiming Ghent threatened to leak embarrassing information and audio and video footage of his sex life to the press.

He was placed under cross-examination on Friday afternoon, when he was forced to admit he had cheated on Ghent with multiple women during their engagement because they were no longer "sexually compatible".

Howard also confessed to having had a sexually transmitted disease, but insisted he wasn't sure if he passed the virus on to her or vice versa, and then revealed he was so desperate to end the relationship with Ghent in 2009, he lied about wanting to take his own life by "pretending to swallow a bottle" of Valtrex pills, medication prescribed to treat herpes.

However, Howard told the court he decided to press ahead with the marriage in 2010 as he attempted to become a Jehovah's Witness and reign in his sexual urges. The union ended a year later (11) and their divorce was finalised in 2013.

He went on to deny allegations of domestic abuse, insisting Ghent was the one who lashed out at him in a jealous rage, hurling food at him after he filmed a passionate kissing scene with his Winnie Mandela co-star Jennifer Hudson in South Africa.

The case continues.

Howard is now married to model/restaurateur Mira and they welcomed their first child together in May (15).