Parks, playgrounds and pitches sold by London councils
Parks, playing fields and allotments equivalent to the size of 67 football pitches have been sold by London councils over the last three years.
Figures obtained by the BBC have shown that an area of open space bigger than Green Park and St James's Park combined has been lost from public ownership.
Local authorities recouped almost £70m from the sales, which came as many councils battled funding cuts.
Councils said the money was used to build new facilities such as schools.
The data, collected using Freedom of Information (FOI) requests, shows that almost 120 acres (50 hectares) have been sold or are currently going under the hammer.
Purchasers have included housing developers and private residents, with many areas of land having permission to be built on.
The sell-offs were criticised by campaigns including the Queen Elizabeth II Fields Challenge.
The campaign, which has Prince William as a patron, seeks to permanently protect open space for the Diamond Jubilee.
Chief executive Alison Moore-Gwyn said the figures "paint a disheartening picture for those who live and work in London".
"There is finite provision of outdoor space in this country, particularly in cities, with London a prime example," she said.
In total 69 open spaces will have been sold but councils have said there would still be some public spaces provided on any new development.
Paul Bramhill, chief executive of parks charity GreenSpace, said: "Local authorities are in a difficult situation - budgets are reduced and green space management is being severely affected.
"We hope the loss of these spaces isn't a knee jerk reaction to raise funds."
He added that green spaces should be safeguarded as once they were built on, it was difficult to reclaim them.
'Surplus to requirements'
The largest space to be sold was an area containing former playing fields which was 80,000 sq m (860,000 sq ft) in size.
Conservative-run Bexley Council is selling it to Redrow Homes, with a price yet to be disclosed.
A council spokeswoman said: "The former playing fields have been classed as surplus to educational requirements for 16 years.
"The receipt from the sale will be used to develop new facilities, which it's proposed will include a multi-use games area and indoor community space.
"Development proposals from Redrow Homes include a ball court and open space with children's play area."
Under the proposals the redeveloped site would have 11,000 sq m (120,000 sq ft) of outdoor space for residents.
Bexley Council said the sale meant it could invest £8.5m in new facilities and extra school places.
Another 48,500 sq m (520,000 sq ft) piece of open space formerly used as playing fields is for sale elsewhere in the borough. The council says it does not envisage a change of use.
Barnet Council, also Tory-run, is selling eight areas - more than any other London council.
They include a pitch, museum garden, playground, school land and Hendon Football Club Stadium.
A council spokesman said: "This is a well planned use of public assets.
"Sales are intended to provide residents of the borough with two new school buildings, at least one sports facility, a recycling centre, two nature reserves, new housing and a children's hospice."
Islington Council, currently Labour-run, sold a playground belonging to the former Moorfields School to Southern Housing Group for £8.3m.
The authority's advert for the sale heralded the playground as a "major investment opportunity", and a "prime city fringe site with potential for residential and office accommodation".
The council said pupils were incorporated into other schools and use their playgrounds.
It was run by the Liberal Democrats at the time of the sale.
Labour MP Kate Hoey, who has campaigned to protect green space, said it was important to study each transaction closely, as some may retain an element of open space.
She said: "If a playing field is sold to a developer who intends to build upon the entirety of the site then this is to be condemned in the strongest possible terms."
London Councils, an organisation that promotes the interests of London's 33 councils, has declined to comment.