Social care could be brought under the control of the NHS in England in a controversial move that would cause the health service’s budget to soar to £150bn, the Guardian has learned. Downing Street has drafted in David Cameron’s former policy chief Camilla Cavendish to help finalise proposals designed to honour Boris Johnson’s pledge to “fix the crisis in social care”. Under plans being examined by Cavendish and ministers, the government would take responsibility for social care services away from councils in England – together with the £22.5bn in annual funding – and hand it to the NHS, the Guardian understands. On Monday night the Department of Health and Social Care (DHSC) denied it had plans to merge the two public services. The proposed merger would be designed to make it easier for frail older people, as well as vulnerable children and the disabled, to access the care they need and ease the strain on an overburdened NHS. Social care is beset by problems including a postcode lottery in the quality and availability of care, workforce shortages and the growing unviability of many providers following a decade-long Whitehall squeeze on councils’ budgets. That has deprived more than 1 million elderly people of care they would have received before 2010. But local authorities are likely to fight merger proposals. Providing social care has been a key role and source of funding for local government for decades. One health policy expert said NHS control of social care would “decimate local government finances”. Cavendish and Helen Whately, the minister at the DHSC with responsibility for social care reform, are examining a plan whereby those services would be commissioned by – and their budgets controlled by – embryonic regional NHS bodies called integrated care systems (ICSs). However, legislation would be needed to implement such a change, not least because ICSs, which bring together different NHS providers of care in an area and are the brainchild of the NHS England chief executive, Sir Simon Stevens, still have no legal standing. The Guardian revealed this month that Boris Johnson was planning to take back significant control of running the health service from NHS England, which may include making ICSs legal entities, a policy backed by the health secretary, Matt Hancock. The duo have held recent meetings with health and care thinktanks and organisations to discuss whether social care should be switched to the NHS or stay with local councils. Whitehall sources say that the prime minister is determined to fulfil his promise to “tackle the injustice of social care” and put in place a new funding system to “give every older person the dignity and security they deserve”, including peace of mind that they will not have to sell their home to pay huge care home fees. The Guardian disclosed on Sunday that over-40s may have to pay more in tax to meet that cost, as they do in Japan. Proponents of fully integrating health and social care, including Cavendish, believe it would lead to people receiving more streamlined care and no longer having to deal with an array of changing carers from different organisations, such as councils, care companies and NHS bodies. Cavendish has criticised a “shocking” lack of continuity in care and cited the example of a man who was visited by 102 different carers. Cavendish, who Cameron made a life peer in 2016, is an expert on health and social care. She has written an acclaimed book on the challenges presented by the ageing population, conducted a review of healthcare assistants for the government in 2013 and has been a visiting fellow at Harvard. The former Times and Sunday Times journalist has described social care as “a system at breaking point” and noted that “failing social care is pulling everything down with it” and causing major problems for hospitals. She supports over-40s funding social care and has proposed that everyone in that age bracket pay extra national insurance for that purpose, including over-65s, who are currently exempt from it. She also favours making personal care – services delivered in older people’s homes – free in England, as it already is in Scotland. Labour proposed the same policy in last year’s election. Johnson has set up a taskforce of advisers and officials from No 10, the Treasury and the Department of Health and Social Care (DHSC) to advise him on how to overhaul the NHS and social care and deliver on promises including expanding the nursing workforce by 50,000 and building 40 new hospitals. Experts warned that a merger would create problems for councils and the NHS. Nigel Edwards, the chief executive of the Nuffield Trust, said: “We would have several concerns about a radical shift of powers away from local authorities to put the sector under the control of larger NHS bodies. These large areas [ICSs] might be a bit remote to really understand what’s going on in social care. They also don’t really exist as institutions yet, so giving them huge new powers as they start up would be a dramatic and potentially disruptive shift for both the NHS and councils. “There would be a risk that this makes social care less joined up with other council services vulnerable people rely on, like housing and public health.” Harry Quilter-Pinner, an associate director of the IPPR thinktank, said: “At its best, integrated care can overcome fragmentation and deliver better outcomes for older people. But policymakers have been talking about delivering integrated care for decades. The truth is it is hard to achieve and stripping local government of its responsibility for social care is a controversial way of going about it. “It would decimate local government finances and without a significant uplift in spending and radical reform to the type of care delivered, there is no guarantee the NHS would be able to do a better job.” One member of the government’s social care advisory panel, who asked not to be named, welcomed Cavendish appointment, saying: “Downing Street bringing her in shows that they are finally going to do something about social care.” The Local Government Association (LGA), which represents councils, warned ministers not to push ahead with a merger. “Shifting responsibility for care is not the answer and will fail to address the fundamental issues that have pushed the system to breaking point. Social care deserves parity of funding and esteem with the NHS, not to be taken over,” said Cllr James Manieson, the LGA chairman. “It is councils and their local partners who remain best placed to ensure everyone has access to personalised support to meet their needs, and must be backed up by a long-term, sustainable funding settlement for adult social care.” A DHSC spokesperson said there was no foundation to the claims. Downing Street was also approached for comment.