The US socialite, who is pregnant with the music mogul's first child, is upset Mezhgan Hussainy - whom he was engaged to for 18 months up to September 2011 - is still part of his life and stepping out with him at social events.
A source told Closer magazine: ''Mezhgan is still his make-up artist, but Lauren doesn't appreciate how she hangs around Simon all the time when it's clear that he's moved on. Simon and Mezhgan sometimes spend 10 hours a day when he's working.''
Lauren is said to be keen for Simon to ditch his whole 'harem' of ex-girlfriends - which also includes Sinitta, Jackie St. Clair and Terri Seymour - so he can concentrate on their new life as a family.
The source added: ''Lauren's told him she wants to be in a normal relationship, without the other women hanging around.
''She also thinks that Mezhgan has been making more of an effort with her appearance lately and Lauren's told him he's got to get her off the scene. It's a big dilemma for Simon as he doesn't like being told what to do and loves Mezhgan's company, but he's serious about wanting to make a go of things with Lauren and the baby.''
Earlier this week, Sinitta admitted Simon's annual vacations with his former lovers could end if Lauren decides she doesn't want them to happen anymore.
Sinitta, 49, said: ''It might change if it is what Lauren wants. I think Simon's quite a creature of habit, he has his traditions, and maybe we'll continue. But he has his own partner and his child with him as well. I could imagine in his mind he'll be thinking, 'We just have a bigger family now.' ''
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