Andrew Lansley has had to stall a major policy announcement on the future of social care for the elderly because Downing Street fears that it could turn into a political disaster on the scale of the health and social care bill.

The Observer has been told that No 10 has "seized the reins" on social care from Lansley, the health secretary, and called in experts to ask their views on what should be in a much-delayed white paper. "No 10 know they have to ensure this is not another disaster like the health bill," said one.

One of the concerns is that plans to give more elderly people their own "personal budgets" – sums of money with which they can buy in social care from private providers – might open up the government to more damaging accusations of the "marketisation" of health services.

The news comes as more than 1,000 older and disabled people from across the country prepare to travel to London on Tuesday to call on their MPs to end the crisis in social care. The lobby of parliament has been organised by the 60 organisations that make up the Care & Support Alliance, including Age UK, Mencap, Scope, the MS Society, Macmillan Cancer Support, Sense, Rethink and Carers UK. The alliance argues that chronic underfunding of social care, combined with rapidly growing demand for care and cuts to local government budgets, has left the system in crisis.

The white paper on the future of social care was originally expected early this year. MPs were then advised that it would be published in March. Now sources at the Department of Health say it will not be produced until "late spring".

The delay caps a miserable two months for Lansley, during which time much of the medical profession has lined up to demand that his health and social care bill – which would devolve power to commission services to GPs and open the way for a greater role for the private sector – be scrapped. Downing Street is dismayed at the political damage inflicted on the coalition by the row and, in large part, blames Lansley for failing to explain the bill's purpose to the public and medical profession. Officials close to David Cameron also accept that No 10 paid insufficient attention to the plans before they were launched in a white paper in 2010. Now, sources say, they are determined to avoid a repeat of the fiasco when a white paper is published, and legislation then framed, on social care.

Last month, the all-party select committee on health, chaired by Stephen Dorrell, the former Tory health secretary, dealt Lansley serious blows when it produced two reports that suggested his NHS reform programme failed to address adequately the most pressing health problem – that of how to deliver affordable and effective social care for the growing elderly population.

The committee suggested that there needed to be far closer integration of the health and social care systems than was currently envisaged, so that more elderly people are treated and cared for at home and are not left until they require expensive and long stays in hospital.

Such views have been registered in Downing Street. Lansley's plan to give every eligible person a "personal budget" through a direct payment by April 2013 has also raised concerns. Under the plan, first introduced by Labour, people's needs are assessed by local social services. They are then allocated a budget, paid as a direct cash payment, with which they can buy care. Currently, personal budgets cover 340,000 people.

Opponents of the system argue that personal budgets will be inappropriate for huge numbers of elderly people who will not be able, or want, to manage their own funds, particularly at times when they are in greatest need of care. Critics also say people's needs will change and the system may not allow them to switch providers quickly enough if contracts have been signed.

With the government also having to address the issue of how to fund social care, MPs believe the social care white paper could even be delayed until after the summer, when Lansley is expected to be replaced as health secretary.

Problems over the health and social care bill now passing through parliament will mount next weekend when Liberal Democrats debate an emergency motion calling for it to be scrapped.