The Tubney Charitable Trust has pledged to double every £1 raised by runners for Help the Hospices in the Flora London Marathon 2005, up to a maximum of £1m.
Help the Hospices is the official charity for next year's marathon and the match-giving arrangement is a first for the event.
The money will be used to develop 'Care for the carers of the terminally ill', a major national programme to support families, friends and loved ones who care for people suffering from a terminal illness. It is estimated that there are around 570,000 such carers in the UK.
This is the largest investment in this field in the UK to date and builds on Caring for Carers, the package of support for carers sponsored by Tesco.com, which was launched in June.
Jonathan Burchfield, chair of the Tubney Charitable Trust, said: "Anyone who has cared for a loved one in the final stage of their life has experienced the desire to provide them with the very best care, and knows of the emotional, financial and psychological strain that doing so may cause."