The SNP was accused of embedding government officials into the heart of family life today, after its plans for child guardians were attacked by parents and legal groups.

Alex Salmond's party plans to give all children in Scotland a state guardian – usually a social worker or teacher – from birth to the age of 18 to monitor how the child was being raised.

"It is obvious many MSPs [members of the Scottish parliament] are not aware of the more sinister aspects of this legislation," Alison Preuss, secretary of the Schoolhouse Home Education Association, said.

"It is open to abuse and misinterpretation and many parents could fall foul of overzealous agents of the state or people who are just plain busybodies."

The guardians, who are defined so widely they could effectively be anyone who is not the child's parents, would be responsible for ensuring the child's upbringing is in line with state-approved standards and of reporting any problems to the authorities.

There are concerns that children could complain to the guardian when they are angry with their parents, potentially triggering a state response.

Hundreds of parents have signed a petition demanding the government U-turn over the policy.

The Law Society warned the move could contravene Article 8 of the European Convention of Human Rights (ECHR), which protects a "private and family life".

"It could be interpreted as disproportionate state interference. We are also unclear about how this legislation will work in practice and in particular, the resources required to administer the 'named person' scheme," Morag Driscoll, convener of the society's family law committee, said in a written submission.

"There is scope for interference between the role of the named person and the exercise of a parent's rights and responsibilities."

The £138million-a-year plans are part of the children and young people bill, which also allows children's personal details to be recorded, stored and shared on a central database. MSPs will vote on the bill later this year.

"The named person, who is likely to be a health visitor, head or deputy head teacher and will usually already know the child, will be a first point of contact if help is needed," a Scottish government spokesperson said.

"This is formalising what should already happen and there is evidence it is working well in many areas."