It could be used to keep a record of information including whether a person has been treated for cancer, to if they have signed up for membership of Edinburgh’s Royal Botanic Gardens.
Opposition parties have voiced “Big Brother” concerns that it is an “intrusive” tool which will increase the “over-mighty power of the state”.
The Scottish Government is considering an extension of the NHS central register, which is already the “most complete and authoritative record of individuals in Scotland”.
It currently covers about 30 per cent of people, but ministers want to extend this and share information stored with more than 100 government agencies – including HMRC for tax purposes.
A similar population register was ditched south of the Border when controversial and expensive plans for ID cards were scrapped in 2010.
Liberal Democrat leader Willie Rennie said: “People hate the idea of ID cards. They would be intrusive, expensive and increase the power of the over-mighty state. They were rightly scrapped in the rest of the UK. It relied on a giant identity register keeping track of all of us.
“It’s a big concern the Scottish Government is building the skeleton of a national identity register in Scotland. It’s one skip away from a ID card and it needs to be stopped. They are planning to take information on people using the health service and allow access to 120 other organisations.”
Scots can access online public services in local government and the health service through a “myaccount” system.
The government now wants all public bodies to use this system and – where they hold information on an individual – to have access to their citizen reference number (UCRN) and be provided with data from the central register.
Mr Rennie added: “We have no information on how SNP minsters would propose to keep information safe.”
The Scottish proposal for IDs linked to a central register was rejected by the Cabinet Office for the rest of the UK as being too high risk and critics said there was no explanation why a central register is not high risk in Scotland.
There are also concerns the plan could breach the Human Rights Act right to privacy, and the Data Protection Act’s requirement that data needs to be “necessary” for it to be retained.
The Scottish Government said that the “minimum amount of data” would be shared, in its consultation. “Organisations will also have to set up data-sharing agreements to ensure that the data is used for the specific purpose identified,” it added.
A Scottish Government spokesman said: “The proposals are consistent with the Scottish Government’s data management and privacy principles.
“We take the security and privacy of this data very seriously indeed, and any sharing would only take place under tightly controlled arrangements.”