In a joint statement the two organisations said they plan to join within a new charitable public corporation which would fundraise for and manage the capital's eight Royal Parks.
The proposal has already won the backing of the government and the Mayor of London. Detailed plans are now being worked up, and it is hoped the new organisation will be established in 2016.
At present The Royal Parks is an Executive Agency of the Department for Culture, Media and Sport (DCMS). The board is appointed by the Mayor of London in conjunction with the Secretary of State. The Royal Parks Foundation is a separate charity which raises funds for the care of the parks as well as educational and heritage projects.
The Royal Parks has seen its Government grant of £18.8m slashed by more than a third since 2010, and was expected to be generating around 75 per cent of its own income by 2015-16.
The statement explained the new corporation will have "increased freedoms", with controls similar to a charity rather than a government department.
"This means the parks can be managed more efficiently while maintaining visitor satisfaction. Placing fundraising and managing the parks under one organisation will also attract stronger funding support."
Running the parks costs around £36 million a year, 65 per cent of which is raised through sponsors, donors, events, catering, grants, lottery funding, licences, rental income from lodges, filming and photography. The Royal Parks have more than 77 million visitors a year with a public satisfaction rate of 98 per cent. But decreasing government funding means maintaining this high satisfaction rate is challenging, the statement added.