London's major parks could close if people do not maintain social distancing rules as lockdown restriction are eased.
Bodies responsible for maintaining key open spaces in London published an open letter on Wednesday, warning rules must be followed if parks are to stay open.
From Wednesday lockdown rules will start being eased.
The government has previously said green spaces should close "only as an absolute last resort".
From Wednesday, people in England will be allowed to take part in more outdoor activities, and exercise as much as they want.
However, people will still need to follow the social distancing rules by keeping more than 2m (6ft) apart from anyone they do not live with.
Since the start of lockdown many local authorities have taken the decision to close parks and green spaces that have become too crowded.
In London the Queen Elizabeth Olympic Park, Lee Valley Regional Park Authority, Parks for London, The Royal Parks, Canal and River Trust and the City of London Trust have joined forces to set common rules during the pandemic.
In a statement the group said: "Social distancing remains.
"Sitting outside is allowed - but keeping your distance from those not in your household.
"It might be that on occasions those working hard to keep these spaces open will ask people to move on as areas are getting too crowded.
"Please respect that and be kind in your response as they are only doing their job to keep open spaces safe.
"We ask you to support us so we don't risk losing these opportunities."
Information on what facilities are open and closed and how they should be used will be placed in each park, the group added.