After the Government's in-year cuts announcement, the organisation, which represents the capital's 32 boroughs and the City of London, warned that councils may soon be unable to support volunteer groups.
Council budgets have been cut 47 per cent in real terms since 2010 and in the past four years boroughs' spending on open spaces, allowing for inflation, has fallen by 18 per cent, with a drop of more than 10 per cent in 2014-15 alone. There are fears across the sector that parks are approaching a tipping point, said the organisation.
London Councils transport and environment committee chair Julian Bell said the climate of austerity means parks will continue to feel the financial strain on their resources. "By harnessing the time and expertise community groups offer, we have been able to continue caring for these precious areas of green space for relaxation and play," he explained.
"There is now real doubt about whether or not councils will be able to support these groups as boroughs divert what money they have to meet statutory responsibilities such as public health and elderly care."
Bell said if the funding problem passes the tipping point: "Communities risk losing control of parks, along with democratic accountability for the open spaces that they value so much". One group facing an uncertain future is the Streatham Common Co-operative (SCCoop), which looks after the common - in the London Borough of Lambeth - aiming to make its management more accountable to locals.
SCCoop chair Richard Payne said the group plans to expand across more local parks in 2016 and to provide benefits such as meeting local health needs and generate income from partnerships and events. All income is reinvested locally.
But Payne warned: "SCCoop has much lower overheads than a typical provider as we have a pool of volunteers to draw on, but even so the level of cuts that are planned will challenge us and it is hard to see how all services can be maintained."
Streatham Common Group under threat
SCCoop grew out of the Friends of Streatham Common. It was formed in 2013, with a £20,000 budget from Lambeth Council's Co-operative Parks Programme allowing the group to get established, hire staff and make initial capital expenditure.
In February 2015 it took over management of the Rookery. It aims to take on management of the rest of the common in 2016 once the council's current contract expires. This year the council allocated £1m to develop the playground and other facilities from the Lambeth Capital Investment Fund.
Volunteers help maintain the horticulture and wildlife of the area and the group recently won a Heritage Lottery Fund grant.
Projects being considered include composting with Lambeth Mencap and a plant-growing project for adults with intellectual disabilities, partnering with charity L'Arche.