City of Trees plans to transform the post-industrial site, to be known as City Forest Park and comparable to New York's Central Park in size, bringing social, environmental and economic benefits.
Straddling the local authority areas of Salford, Bury and Bolton, it is connected by the river Irwell and by road and cycleway to Manchester city centre.
It first received funding in 2007 from the Government's Newlands programme via the Forestry Commission to create a series of interlinking path networks, and plant thousands of trees. The site is currently home to 250,000 trees, as well as meadow heath and wetland.
City of Trees director Tony Hothersall said: "With the right investment, we will be able to realise City Forest Park's full potential and give the region the inspiring green space and culture hub it deserves and needs."
The charity says it will work with local partners to organise events ranging from pop-up markets to theatre performances, picnics or cycle rides. Architect BDP has drawn up artist's impressions of how the site could look with phased investment.
Established last year, City of Trees is funded by The Oglesby Charitable Trust and the Community Forest Trust, and lists nearly 50 partners including the Greater Manchester Combined Authority, Transport for Greater Manchester, Natural England, the Forestry Commission and the Woodland Trust.
On 22 September it held a seminar for over 100 developers, landscape architects, planners, engineers and regeneration workers on the importance of urban greening in the area.