The controversial new Tom Cruise biography may go some way to explaining why Nicole Kidman’s adoptive children call Katie Holmes ‘mom’

Andrew Morton claims in his book, Tom Cruise: An Unauthorized Biography, that Nicole has played a more or less absent role in the lives of Isabella, 15, and Connor, 12.

Morton writes: "Those who saw the family close up concluded that Tom was much more comfortable and enthusiastic as a parent. The actor was in constant - and controlling - touch with the youngsters and their nannies no matter how busy he was."

The author also alleges that Nicole would go for days without calling her children when she was away filming on location.

He says: “[It] could be days before she would phone to see how Isabella and Connor were coping.”

In November last, Nicole told U.K.'s GMTV: “My kids don't call me mommy, they don't even call me mom. They call me Nicole, which I hate and tell them off for it."

Meanwhile Katie revealed to Parade magazine: "[Tom’s] first two children are incredible, really smart and kind. They call me 'Mom.' So Tom understands the female bond, and he loves it."

Nicole announced earlier this month that she is expecting her first child with husband, Keith Urban – let’s hope she doesn’t just phone in her performance this time round.