Social services departments will have to show that care will be maintained during peak "winter crisis" periods to earn their share of an extra £100m earmarked by health secretary Alan Milburn.

The ring-fenced grants of up to £2.6m each come with several strings attached, including a requirement that financially stretched departments cannot use the cash to hide financial problems.

The £100m grant was announced by Mr Milburn yesterday, as it emerged that an official survey had revealed more investment was needed to strengthen health and social services winter planning.

The Department of Health's Winter Plan says the "majority" of health authority areas have been classified as at "low to medium risk" of winter problems.

But it added that there was a "need for additional resources to build extra capacity in some parts of the country, particularly at the interface between health and social services". And it warned that shortages of social services staff, as well as health staff, was a problem: "The supply of staff required to deliver the NHS plan cannot be found immediately."

All social services departments have developed local plans with the NHS to maintain services at peak times during the winter and ensure elderly patients are promptly transferred from acute hospital beds to community care when clinically appropriate.

The report did not identify which areas had been assessed as "high risk" of service problems developing over the next few weeks.

The extra £100m has been added as a top-up to the Promoting Independence grants announced earlier this year and will be paid directly to those councils that can demonstrate the money will be used effectively.

A DoH letter to local authority chief executives warns that the grants, which range from £332,000 (Merton) to £2.65m (Kent) cannot be used to ease general social services budget deficits. It says councils will also have to demonstrate specific improvements in service delivery and performance, and effective joint plans with the NHS and other partners.

The government insisted that social care has sufficient resources to cope with the winter pressures, including over £100m invested in intermediate care to ensure acute hospital patients can be moved into the community. It says that early indications show there has been an increase of 2,900 intensive home care packages in the year to September 2000, and 6,700 more local authority supported places in residential and nursing homes in the 12 months to March 2000.

Although the private care homes sector cut 7,300 beds in 1999-2000, ministers insist that its investment in intermediate care will "more than offset" this reduction.