Ministers have written to thousands of solicitors asking them to prompt clients to leave money to good causes in their wills.
The move is part of Remember A Charity In Your Will Week, which starts today.
Rob Wilson, the Minister for Civil Society, Damian Hinds, the Exchequer Secretary to the Treasury, and Paul Wheelhouse, the Scottish government’s Minister for Community Safety and Legal Affairs, contacted more than 8,700 solicitors.
The letter describes legacy giving as "fundamental to the amazing work of many charities".
"Many charities rely on these gifts to help them carry out their vital work," it says.
"Unfortunately there is evidence of a disconnect between people’s intentions to give money in their wills and those doing so.
"You can help make sure your clients include everything they want to in their will by simply reminding them that leaving a gift to charity is an option. Your support can make a huge difference this Remember A Charity In Your Will Week."
Ed Vaizey, the culture minister, has also asked cultural organisations to get involved in raising awareness this week.
Research by the Behavioural Insights Team has showed that prompts from solicitors can treble the number of gifts made to good causes, said Remember A Charity, the group of more than 150 national charities that runs Remember A Charity In Your Will Week.
Rob Cope, director of Remember A Charity, said: "Never before has the campaign achieved so much support from government and the legal profession, and this is critical to extending our reach to new audiences and to achieving social change."
He said the group’s research showed that although 35 per cent of people in the UK were happy to leave gifts in their wills, only 7 per cent did – despite this, the group said, charitable bequests were the largest single source of voluntary income in the UK, generating more than £2.2bn last year.
Cope said: "Particularly in light of the negative portrayal of fundraising in the media recently, it has never been more important that charities continue to strive for the highest standards, cherish their supporters and celebrate success.
"Without legacy giving, many charitable services might not survive."
The Remember A Charity In Your Will Week awareness campaign will also include an online documentary featuring "extreme will writers" – people in their sixties and above signing their wills in an aircraft at 10,000ft before completing a skydive.
The campaign slogan is: "You don’t have to go to extremes to become a living legend; you can just leave a gift to charity in your will". Charities are being encouraged to celebrate their donors on Twitter using #LivingLegend.