David Cameron has been urged in an open letter by a group of leading charities to transform the provision of care for the elderly.

A coalition of 78 charities and campaign groups have warned the Prime Minister that unless he acts, millions more pensioners will be condemned to a life of ‘misery and fear’.

The Prime Minister was also warned that many years of failure to reform the system has had a ‘devastating impact’, not only on those in need of care, but also on their relatives, who can be forced to give up their jobs to look after a vulnerable family member.

Pensioners with savings or assets worth more than £23,500 have to pay the cost of their own care under the current system. However, Andrew Dilnot, Cameron’s government commissioned economist, believes that the cut off should be £100,000.

A much-delayed White Paper on long-term care will be published in June, but it will focus on the quality of care provision, with the issue of paying for it relegated to a "progress" document. It was also emerged that a new funding system may not be fully in place until 2025.

Charities have been left outraged by the delay as it would condemn thousands more pensioners to having to sell their homes, denying their children an inheritance. It is also estimated that at least 20,000 pensioners have to sell up each year to meet care costs.

Anne Roberts, chief executive of the Carers' Trust, told BBC Breakfast: "We are calling on the Government to take this opportunity to look at how social care is funded and to look at how you better join up health services and social care... There is a real opportunity to reform social care and we really are asking the Prime Minister to take a lead on doing that."

Last night a spokesman for the Department of Health said: "We absolutely agree that the social care system is in need of reform. We will publish our White Paper on care and support shortly and are working hard to secure cross-party agreement to find a sustainable long-term solution on social care funding."

The open letter to the Prime Minister, which has been signed by charities, trade unions and local government organisations, was organised by the Care and Support Alliance.

Its signatories include organisations dedicated to the elderly, such as the English Community Care Association, Grandparents Plus, the British Geriatrics Society and Action On Elder Abuse. It has also been signed by a range of medical organisations including the British Medical Association, the Royal College of Nursing, the British Red Cross, the Stroke Association and Macmillan Cancer Support.