A legal challenge against Scottish government plans to appoint a "named person" for every child in Scotland is being heard at the Supreme Court.
Four charities and three individuals have lodged an appeal against the scheme, which is due to come into force in August.
The plan is part of the Children and Young People (Scotland) Act 2014.
Ministers believe it will help protect children, but critics have said it will create a "nanny state".
The scheme would allow the named person - usually a senior teacher - to provide advice, information or support where appropriate to promote, support or safeguard the wellbeing of youngsters under the age of 18.
The court has been asked to decide whether the provision is compatible with fundamental common law rights and the European Convention on Human Rights.
The case is being brought by three individuals and the Christian Institute, Family Education Trust, The Young ME Sufferers ("Tymes") Trust and Care (Christian Action Research & Education).
In September of last year, the Court of Session dismissed the campaigners' arguments as "hyperbole".
However, they are hoping to convince the Supreme Court that the act authorises "unjustified and unjustifiable state interference with family rights".
'Scrapping or redrafting'
Speaking ahead of an expected two-day hearing which started on Tuesday, Care's Dr Gordon Macdonald said: "The Scottish government's named person scheme is very dangerous and will undermine parents and their role as the best guardians of their children.
"Simple logic dictates if you spread resources too thin, which this scheme will inevitably do, vulnerable children who are most in need of help may well be overlooked and put at risk.
"We have brought this case to the UK Supreme Court because it has the power to overrule the Scottish government and also because we remain utterly convinced this scheme breaches international human rights laws and therefore needs to be scrapped or redrafted.
"There is a growing sense of alarm in Scotland at the plans. If introduced, the state would be assuming too prominent a role in the raising of young people."
But the scheme has received support from many leading children's charities and organisations such as the Scottish Secondary Teachers Association (SSTA).
The union's Seamus Searson said: "A named person helps children and families get the right support at the right time from the right people.
"It does not replace or change the role of parents and carers, or undermine families."