Ministers said the proposals would end the “postcode lottery of care in Scotland”, with health secretary Humza Yousaf insisting: “This is the most ambitious reform of public services since the creation of the NHS.”
But opposition politicians and union leaders condemned the plans, with Unite calling them an “all-out assault on local democracy”.
Legislation for the social care overhaul was published by the Scottish Government as it aims to change the way care services are accessed and delivered.
The Bill will make ministers accountable for adult social care in Scotland.
Councils will no longer run social care services, while “care boards” will be created to fulfil a similar function to existing health boards.
Ministers said the new service, which is set to be up and running by 2026, aims to support people in their own homes where possible.
A charter of rights and responsibilities will be developed with a “robust” complaints process in place.
Unpaid carers will have the right to breaks under the plans, while visiting rights for residents living in adult care homes will be introduced, giving legal force to Anne’s Law, which seeks to reduce the trauma caused to families unable to see their loved ones during lockdowns.
The proposals also aim to ensure fair employment practices and national pay bargaining for the social care workforce.
But Unite general secretary Sharon Graham said: “The Scottish Government could not have drafted a more incomprehensible, incoherent and dreadful Bill.
"The plans to transfer services, people and property from local authorities to the Scottish Government are a recipe for disaster and represent an all-out assault on local democracy.”
Documents suggest the total estimated cost of the Bill’s provisions could be up to £1.26bn over the next five years.
Establishing a national body could cost up to £496 million, while establishing care boards could cost up to £726m.
Scottish Conservative social care spokesman Craig Hoy said: “Social care provision in Scotland is in crisis.
"But the last thing we need right now is a major bureaucratic overhaul of the system which would see precious resources diverted away from the frontline and into employing hundreds more management and admin staff.
“The SNP Government’s own figures show that establishing a National Care Service could cost an eye-watering £1.3bn in administration costs.
"We simply can’t afford to see that sort of money diverted from frontline local services.
“The plans to create a National Care Service will just be a repeat of Police Scotland on an even larger scale, which led to years of scandal, financial problems and leadership crises.”
SNP social care minister Kevin Stewart said the Tories’ claims “wilfully misrepresent the investment that is planned for the National Care Service”, adding: “These costs largely represent investments in service improvements and terms and conditions for frontline care staff.
"Any suggestion that the figures relate exclusively to ‘admin costs’ are totally false.”
Scottish Labour deputy leader Jackie Baillie branded the plans “nothing less than the biggest power grab in the history of Holyrood – one that threatens the very existence of local government in Scotland”.
She said: “After years of steadfast opposition to a National Care Service, the SNP is now using the creation of such a service to disempower local government and centralise yet more power.
"The wholesale transfer of over 100,000 staff away from local government is a recipe for chaos and uncertainty and people receiving services may suffer as a result.
“Make no mistake – this is not a National Care Service. What the SNP and their friends in big business have devised is a national commissioning service which can be used as a fig leaf for centralising power.”
Scottish Liberal Democrat leader Alex Cole-Hamilton said the new legislation “amounts to nothing more than an SNP takeover and a top-down reorganisation of care”.
He said: “Just as with the police, it will waste money and reduce services.
“It would be terrible for care services if authority was to be taken away from local councils and permanently handed to the same Scottish Government ministers who were responsible for sending untested and Covid-positive patients into care homes at the start of the pandemic.”
Mr Yousaf said: “People have told us they want a National Care Service, accountable to Scottish ministers, with services designed and delivered locally.
"That’s exactly what we are going to deliver.
“The design of the NCS will have human rights embedded throughout, and the actual shape and detail of how the NCS works will be designed with those who have direct experience of accessing and providing social care.
“We are going to end the postcode lottery of care in Scotland.
"Through the National Care Service we’re going to ensure everyone has access to consistently high-quality care and support so they can live a full life.
"This is our ambitious goal and while it will not be easy to achieve, it is vital that we do.”