Scotland's new National Care Service (NCS) may cost up to £1.3 billion to deliver over the next five years but the figure could "change considerably", a Holyrood analysis of the SNP's flagship policy has said.

The warning over changing costs comes at a time of increasing tight public finances with Deputy First Minister John Swinney already announcing £500 million worth of cuts from the Holyrood budget. He has also signalled more savings will need to be found.

Health Secretary Humza Yousaf introduced the National Care Service (Scotland) Bill into Holyrood on 20 June this year with the purpose to improve the quality and consistency of social services in Scotland, better integrate these services into health care and end a "postcode lottery" in the care sector.

He tweeted at the time: "NCS will be most ambitious public service reform in the devolution era. We will look to end the postcode lottery of care and put people - both those who rneed care and our workforce - at the centre of the NCS."

Under plans for the new model a series of new care boards would be set up that will operate in the same way as health boards and will be the direct responsibility of ministers.

However, Labour, and the trade unions have all criticised with both accusing the Scottish Government of “grabbing power” from local authorities.

The Scottish Parliament's briefing published today examined the estimated costs outlined in the government's financial memorandum for delivering the new service and looked at how the costs could change. The independent analysis by Holyrood researchers said it would be appropriate if MSPs were kept informed of the updated figures.

"The total costs of the Bill over the five year period 2022-23 to 2026-27 are estimated at between £644 million and £1,261 million," said the memorandum.

It said there were a range of uncertainties acknowledged in the financial memorandum, the most significant of which include: the range of services to be transferred to the NCS, the nature of the delivery model to be introduced, the phasing of introduction of the new model staffing requirements and the extent to which staff will transfer to new bodies.

The briefing added: "As these uncertainties are resolved, the Scottish Government should be in a position to produce more refined cost estimates. 

"However, these would not receive further scrutiny as decisions would be reflected in secondary legislation which would not have an associated FM....

"This leaves scope for estimated costs to change considerably without any detailed Parliamentary scrutiny, so it might be considered appropriate for updated costs to be presented to the Parliament’s Finance and Public Administration Committee as the Bill progresses through its Parliamentary stages and as further decisions are reached on the scope and nature of the NCS."

Last year an independent review led by former NHS Scotland chief executive Derek Feeley found it would not be possible to “achieve the potential of social care support in Scotland without a new delivery system”.

The service would be expected to launch at the end of 2026, at which point local authorities would no longer run social care services.

Scottish Conservative MSP Craig Hoy said: “This independent analysis confirms the eye-watering costs if the SNP press ahead with their plans for a National Care Service.

“That is crucial funding that will be diverted away from local communities, to the detriment of overstretched staff and patients.

“The centralisation of care services will end up being like Police Scotland on an even larger scale which has led to years of financial problems and a lack of accountability.

“The Scottish Conservatives have been against these plans from the outset and the SNP must abandon these proposals and put every penny into local care services instead.”

Scottish Labour Health spokeswoman Jackie Baillie said: “While social care services are crying out for funding, the SNP are frittering away millions on an unpopular and unworkable power grab.

“They have no vision for social care and no plans to tackle real problems, raise standards or improve pay. Instead they are wasting huge amounts of time and money centralising powers and stripping away local accountability.

"This money should be spent on increasing packages of social care for people in desperate need now, rather than spending it on structures.

“We need a real National Care Service with local delivery, local accountability, and care users and workers at its heart.”

Responding to the bill's publication in June, Unite regional officer Wendy Dunsmore said it represents the “biggest power grab” in the era of devolution, adding that it would be “bizarre” if the plan means responsibility for care is transferred from local authorities to care boards but local authorities are contracted to provide the care.

“Scottish Government ministers will be able to unilaterally decide what services are to be delivered nationally or locally yet there is next to no detail on major elements of these proposals including how local and special care bodies will work independently and with each other even if it's at a minister’s sole discretion,” she said.

“The proposal to make local authorities a contractor for a service they currently provide by one of these care bodies is just simply bizarre.

"Unite has for some time been severely worried about the emerging framework surrounding the National Care Service and we have had every right to be. These proposals will be vociferously challenged and ultimately defeated.”