Ministers have confirmed they cannot commit to a cap on the cost of social care unless they can find an extra £2.2bn at the next comprehensive spending review – and suggested the cap could be higher than the level recommended by an independent review of care funding.

Launching the much-anticipated social care white paper this morning, ministers also confirmed that an extra £300m will be found from NHS efficiency savings to “support the transformation of local services”.

The white paper says the government accepts in principle a cap in care costs, as recommended by the Dilnot Commission a year ago, and will work to introduce a system of “deferred payments” for residential care by April 2015. Ministers will also bring in a national minimum eligibility threshold at the same time.

However, a “progress report” on funding reform published alongside the white paper said “there are a number of important questions and trade-offs to be considered”. A new funding model will only be based on the Dilnot principles “if a way to pay for it can be found”.

“The government is unable to commit to introducing a new system at this stage. Funding reform needs to be considered alongside other priorities and the right place to do this is at the next spending review. A final decision will be taken then”.

The next review is expected in 2015.

Ministers are considering a system with a higher cap than the Dilnot Commission recommend, and allowing people to opt out of the system, potentially shrinking the risk pool and increasing the cost for those in the scheme.

The Dilnot Commission suggested care costs be capped between £25,000 and £50,000 per individual. But the progress report says: “There was a discussion of the level of the cap, with some people suggesting that a cap could be set at the top of the commission’s range – or even slightly higher (eg at £75,000) – without undermining the principles of the system.”

The DH has run calculations for the effect of a cap of £100,000, and has used that model as the assumption for some of its further analysis.

The report says “the financial services industry” had said the “most appropriate level for the cap” might be higher than the Dilnot recommendations. “Others recognised, given the fiscal circumstances, that a higher cap could provide a more affordable way to implement reform”.

Ministers are also considering an “opt-out approach” to the scheme. The report said: “One approach would be to implement a voluntary scheme which people could opt into or out of.

“People could individually make the choice to be protected by the capped cost scheme – and only people that opt in would pay the cost.”

The extra £300m of transition funding will be distributed to councils from the NHS budget via the NHS Commissioning Board. Health minister Paul Burtow said the cash would be sourced from quality, innovation, productivity and prevention efficiencies.

Ministers pledged to publish a framework for improved integration between health and social care.

The white paper will now go to consultation. Ministers have said they will work with the opposition on the plans.