Madonna wants to be a tougher parent.

The 'Masterpiece' singer raises daughter Lourdes, 15, son Rocco, 11, and adopted son David, six, and daughter Mercy, also six, and admits she could be harder on them.

When asked if she is a tough mother, she replied: ''I think I am, but honestly I don't think I'm as tough as I should be. I think I need to be maybe tougher. It's hard though. Everyday is a negotiation.''

Asked about pictures of Lourdes smoking, taken in New York last month, Madonna said she ''wasn't very happy.''

Speaking on US show 'NBC's Rock Center with Brian Williams', she added: ''Cigarette smoking I'm not very fond of, for anyone, I don't approve of anyone smoking cigarettes, most of all my daughter.''

When host Harry Smith pointed out that in the video to her recent track 'Girls Gone Wild' she is seen smoking, Madonna defended herself, saying: ''Yeah, I don't smoke. That's just an accessory, Harry. There's a difference.

''She smoked that cigarette before I did that video, so she didn't' get that from me, OK?''

The 53-year-old star was also asked if there are two versions of her, an off stage one and an on stage version.

She replied: ''There's probably 25, but to my children there's mostly the one that comes home and says, 'Have you done your homework?' and 'Why are you wearing that?' and 'Why did you say that?' and 'What are you eating that for?'''

Madonna's latest album 'MDNA' is out now, and she is preparing for a World tour over the summer.