The Bill approving the SNP’s guardian scheme was passed at Holyrood earlier this year, despite a furious backlash from family groups.
The Scottish Government claims the move will ensure potential cases of abuse or developmental difficulties are spotted and acted upon at an early stage.
But critics have dubbed it a “Big Brother invasion” and warned that it “undermines the role of parents”.
There are also fears that parents could be dragged into damaging child protection probes for trivial reasons.
Every child will be assigned a named person – a health worker or senior teacher – to oversee their upbringing to the age of 18 by 2016.
But medical staff are already threatening to report mothers or fathers if they forget to take their children to hospital appointments.
In a letter sent to one family by NHS Forth Valley, a paediatric consultant wrote: “We are now required to inform the named person for your child if your child fails to attend an appointment.”
It goes on to add: “In addition we may also send them copies of future relevant reports.”
Campaigners, who have already raised £30,000 to fund a legal challenge against the initiative, condemned the development.
We are now required to inform the named person for your child if your child fails to attend an appointmentA letter sent by NHS Forth Valley
“The state seems intent on usurping the role of parents and reducing them to helpless spectators in the lives of their children.
“Mums and dads should be very afraid of this kind of Big Brother invasion into their lives and their homes.”
The Tories’ young people spokeswoman, Liz Smith, said: “It fundamentally undermines the role of parents and families, the vast majority of whom are doing a thoroughly good job of bringing up their children, and who have absolutely no need or any wish to have a named person.”
The policy has been previously criticised for its potential to lead to the targeting of ordinary parents.
Stuart Waiton, a sociology and criminology lecturer at the University of Abertay, has claimed that innocent issues such as what a child eats or the views they express could be used against parents.
He added: “It will take very little to trigger an investigation into a child and from there a false picture can easily be arrived at.”
NHS Forth Valley said that it is using powers already available under the Scottish Government’s Getting it Right for Every Child (GIRFEC) guidelines.
A spokeswoman for the health board: “Under existing legislation organisations are already able to share relevant information if there are any welfare concerns about a child or young person and inform individuals if a child fails to turn up for a health appointment or attend school.”
A Scottish Government spokesman said: “Some areas of Scotland have been using the named person policy for a number of years.
“The Act seeks to provide a consistent approach nationally and to safeguard the wellbeing of all of Scotland’s children.”