The 45 year old, who is mum to Zephyrus, four, and one-year-old twins Xanthe and Zena, told the audience at a recent book launch that her live-in nanny, Jenny, was like a big sister to her children, and that she was 'sensible' about the divide of affection.
'I think as the parent you've got to give your nanny as much autonomy as you possibly can. There are no jealousies - if one of them falls over and goes to her I can't go "oww!" because if I'm not there I need that to happen,' she explained.
'Jenny is like a big sister to the children and she's very natural if we're in the room together. You have to be sensible about it. You can't feel guilty.'
'It's the most important job in the world looking after your children so for me the only way is to have them as a part of your family,' she added.
Julia has previously spoken out about her difficulties conceiving as an older mum. She had her first pregnancy at 41, but having been diagnosed with endometriosis in her thirties, she had to undergo five rounds of IVF in order to conceive her twins in 2014.
'How many rounds of treatment would I have had?' she asked in an interview with You magazine in February 2016. 'Hand on heart, I don't know. I was so driven, so determined to have a sibling for my son, that even I was shocked by the strength of my feelings.'
Despite her struggles with fertility, Julia has previously said that there were advantages to waiting until her forties to become a parent.
'Obviously I'm going to advocate being an older mum but not just because I am one. It would be lovely if we could plan our lives and careers around when we're going to have children but we don't live in an ideal world,' she told the Express during her pregnancy with Zena and Xanthe in 2015.
'The advantage of having children younger is that your body is probably more able but you're generally not so secure in your career, financially or in your relationship. There's no way I could have done my job if I'd had children in my 20s and 30s as I couldn't have travelled the world for work.'
However, she also admitted that motherhood had caused her to change her lifestyle, saying 'In four years I've suddenly become a grown–up. Motherhood has changed everything and it has been rewarding in ways that I had never anticipated.'
'I never thought it would be as fulfilling and I didn't think I'd be as happy to stay in on a Saturday night watching Peppa Pig. If you'd said that five years ago I would have said no.'