The Met was criticised after its handling of the G20 protests in London
Green activists were urged by senior Metropolitan Police (Met) officers to reveal the location of a protest camp to be held in the capital next week.
Around 3,000 people are expected to attend the seven-day event organised by Climate Camp.
Officers said advance knowledge of the location could help smooth relations.
The Met have said they will use "community-style policing" after widespread criticism of police handling of the G20 summit in April.
From Wednesday, organisers intend to "swoop" on an open green space and set up a mini community, complete with neighbourhoods, shops, toilets and daily events.
But one senior police officer said the secrecy is making it difficult for police to prepare.
"A fundamental bit of policing is understanding where it is going to be and when it is going to take place because of the impact they will have on people around them," said Assistant Commissioner Chris Allison.
"I do not know why they will not tell us. I am saying: 'Tell us, or at least tell us the borough.' Let us at least move this forward."
'Police interference'
A spokesman for the Climate Camp group said they were "absolutely not" playing cat-and-mouse with the police but would keep their location secret to prevent "undue police interference".
The Met was roundly criticised for the handling of the G20 protests in April.
The demonstrations were marred by the death of newspaper vendor Ian Tomlinson.
The Crown Prosecution Service (CPS) is now considering whether any criminal charges should be brought.
But the Met said the controversial practice of penning people in for long periods, known as kettling, remained an option.
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