United Kingdom, March 23 -- Ben Foster has accused Laura Prepon of "inappropriate marital conduct".

The 44-year-old actor initially cited irreconcilable differences when he filed to end their marriage last November, but earlier this month, the 'X-Men: The Last Stand' star asked the court to file an amended petition with new details.

In the amended petition, which has been obtained by In Touch magazine, his lawyer wrote: "[Ben] would respectfully show that [Laura] has been guilty of such cruel and inhuman treatment or conduct (i.e.; inappropriate marital conduct) towards [Ben] . which renders further cohabitation unsafe and improper."

Ben has asked the court to enforce the prenuptial agreement they signed on 21 May, 2018, and requested ...