Havering Council is launching an internal mole hunt after leaked papers revealed a proposal to sell off 44 plots of land for housing.
At a meeting on January 24, Conservative councillors heard libraries, community centres, Green Belt and car parks could make way for more than 1,300 new homes, raising £70m.
The papers were anonymously mailed to opposition candidates last month.
A council spokesperson said: "We will be investigating the leak, especially as we were in purdah (pre-election period)."
During purdah, council staff cannot publish information which might influence an election.
The report proposed disposing of 14 social spaces, like community halls and youth centres, with only four re-provided in the resulting developments.
Four libraries were also on the list, of which one would not be replaced.
The council spokesperson noted the report was only put forward for discussion and no decisions have been made.
“It’s unclear what of this has been agreed,” said Gillian Ford, chairman of the Havering Residents' Association (HRA).
She said council rules banned her from discussing details of a "restricted" document, but added if the HRA took power after last week's election, any planned disposals would be reconsidered individually.
“I’ve seen the document and it would be extremely worrying for the borough if these plans went ahead,” said independent Bob Perry, hours before losing his council seat.
He condemned the proposal to sell off car parks, asking: “How is that going to help struggling local businesses?”
Conservative leader Damian White said he did not recall any decisions having been made.
He said last week: “Whilst I am leader, I would never, ever countenance selling off any community centres or libraries, because that would rip out the heart of Havering.
“But it was right and proper, as part of the budget strategy, that we should review it. It’s a regular part of the budget strategy to review it every year.”
Havering Council said: “This was a confidential report put forward by officers for discussion with the administration, that looked at potential options around council-owned assets...
"The future administration will decide on disposals and when decisions are made these will be made public. As no sites have currently come forward, no decisions have yet been made.”
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