The Legacy Promotion Campaign is to launch a television advertising campaign - the first time a charity consortium has used the medium.
The campaign is using the advert, backed by a print media campaign, to encourage people to write or update their wills and include their favourite charity among the beneficiaries.
Entitled 'I will. Will You?' and fronted by Michael Buerk, the 40-second advert will be aired from mid-May on Channel 4.
The campaign's new director, Jonathan Parris, said the adverts emphasise that writing or updating a will is an easy way to benefit both charities and families by reducing inheritance tax.
Parris has been involved with the campaign since it launched in 2002 and was a member of its steering group while also director of fund-raising at Diabetes UK.
New members of the consortium of more than 130 charity members include the Prince's Trust, the Mental Health Foundation and the Born Free Foundation.