Hospitals in Sussex are earning more than £25,000 a year from a promotions company that targets parents on maternity wards.
Parenting network site Mumsnet wants a national ban on letting organisations like Bounty pay for access to departments.
Representatives hand out free samples of items like nappies and skin creams and also offer a photo service.
They also give information about vaccinations, child benefit, smoking, and healthy lifestyles.
However they also collect name and address details which can be passed on to other organisations.
A Mumsnet survey found more than half of new mums said they were not told that giving these details was voluntary.
Fifty-six percent also felt their privacy had been invaded.
Health Minister Dan Poulter has called on all NHS trusts to review their practices when it comes to allowing access on to the wards.
Trusts in Sussex said almost all of its patients were happy with the service given by Bounty.
Brighton and Sussex University Hospitals NHS Trust received more than £20,000 from Bounty last year.
A spokesman said: “Bounty provide a photographic and information service on our maternity units and this is popular with new parents.
“All of their staff are CRB checked, they work under a company code of conduct, and they are not allowed to disturb women without first checking with the postnatal ward staff.”
Claire Morgan, 33, from Hove, used the Bounty service at the Royal Sussex County Hospital in Brighton after giving birth in December.
She said: “New mums are perfectly capable of saying no if they do not want the service so it is nonsense to suggest Bounty are not providing a good service to women.”
Carole Garrick, head of midwifery at Western Sussex Hospitals NHS Trust, which received more than £5,000 last year, said: “We simply would not allow any of our mums to feel pressured by a commercial organisation, and if we received complaints we would act immediately.
“However, we have never had any complaints at all about Bounty, their staff, or their packs. In fact, the only time that mums mention the packs is to ask for one.”
East Sussex Healthcare NHS Trust would not say how much it received, but confirmed it worked with Bounty and had no immediate plans to stop the service.
A Bounty spokeswoman said: “We fully agree that it would be unacceptable for any organisation to share private data without the express and informed consent of mums and that is why Bounty has an extensive code of conduct to ensure that this does not happen.
“As is a legal requirement,mums who do not wish for their contact details to be shared with our partner organisations are always given that option.”