Charlie Sheen custody battle turns ugly as he taunts mother-in-law over cancer treatment

Hollywood actor Charlie Sheen's custody battle took an ugly twist when he taunted his former mother-in-law over her cancer treatment, it has been alleged.

The former Young Guns heartthrob has been battling his ex-wife, actress Denise Richards, for visiting rights to their two daughters.

But with their divorce settlement becoming increasingly acrimonious, he was said to have launched an astonishing attack on her sick mother Joni, who is undergoing treatment for breast cancer.

Happier times: Charlie Sheen and Denise Richards pose for cameras before their acrimonious split

Sheen allegedly told Miss Richards in an e-mail: "You are a pig. A sad, jobless pig who is sad and talentless and, um, oh yeah, sad and jobless and evil and a bad mom, so go f*** yourself, sad, jobless pig."

In another he wrote: "Go cry to your bald mom, you f***ing loser."

The name-calling incident mirrors the ugly split between fellow actors Alec Baldwin and Kim Basinger.

Baldwin, 49, was banned from seeing their 11-year-old daughter Ireland after calling her a 'rude, thoughtless little pig' for refusing to take his phone calls.

Sheen, 42, and Miss Richards, 36, met on the set of the 2001 film Good Advice but ended their four-year marriage in November last year.

Since then they have clashed over custody arrangements for their daughters Samantha, three, and Lola, two.

Miss Richards has previously accused her ex-husband of looking up child porn on the Internet while caring for the girls and of not being capable of looking after them.

She added when they returned from weekends with their father they were 'sad and upset.'

Sheen accused Miss Richards of driving a wedge in his relationship with their children.

She has already won the right to choose two nannies to accompany the children to his home and has applied for a court order to limit their visits to days rather than overnight stays.

The pair have also clashed over the children's medical needs with Sheen refusing to let them have commonplace jabs.

Their ongoing battle caused Samantha's doctor Jeannette Levenstein to resign, saying: "because of differing philosophies I cannot continue to treat her."

Sheen, who followed in his actor father Martin's footsteps, rebelled in his youth.

As one of the Brat Pack during the 1980s, he had a playboy reputation and was exposed as a drug user and regular client of Hollywood madam Heidi Fliss.

Miss Richards has claimed he still has drug and gambling problems as well as still using prostitutes.

Sheen has denied the allegations.