A parenting group has warned that there is a "clear North-South divide" in how often a child sees a health visitor.
According to the Family and Parenting Institute (FPI), there are marked variations between the number of health visitors across the country, particularly between London and the north.
It said this leads to a postcode lottery determining how often a child is seen by English health trusts.
A survey found that County Durham Primary Care Trust had the best figure, with one health visitor for every 165 children under five, but Lambeth PCT had the worst, with one visitor for every 894 children.
The findings show that eight of the 10 PCTs with the lowest number of health visitors were in London.
Chief Executive Mary MacLeod said: "This postcode lottery is unacceptable.
"The value of health visitors is unquestionable. Health visitors respond to parents' worries and concerns, and their unique relationship and position of visiting families in their home means that they can detect problems that parents may not talk about."
In response to the results the FPI is calling for a universal health visitor service and improved training within the profession.