About 30 bags of fly-tipped waste and building materials have been dumped on Wanstead Flats.
Loft insulation, plaster and boards were among the rubbish left overnight at the space which borders Forest Gate, Manor Park, Wanstead and Leytonstone.
It was discovered by passersby on Thursday, May 6.
Chris Austin from Forest Gate said there have been at least three occasions within the past 10 days of this incident when the Flats have been targeted.
Mattresses and black bags filled with soil were plonked at one spot, with another illegal dump opposite the Golden Fleece pub in Capel Road.
"It's awful. It's an attitude: somebody else will clear it up, and they do," Chris said.
He praised the City of London Corporation, which manages the 334-acre site of open grassland, saying it was quick to remove the waste.
But he called for CCTV or concrete blocks to be put up to stop fly-tippers driving onto the Flats.
Chris, who regularly walks his dogs in the area, explained how he often sees people leaving their litter behind.
He speculated a "dodgy, cowboy builder" could have left the latest fly-tip, or maybe someone had paid another person to dispose of the waste but not spent enough to see it dealt with properly.
The corporation reported last year that illegal fly-tipping at Epping Forest had increased by more than 50 per cent.
Wanstead Flats forms the southernmost part of the forest, which comprises 2,400 hectares of ancient woodland, straddling the border between Essex and London.
It is also a site of special scientific interest and home to Jubilee Pond.
Between January and April 2020, there was a total of 192 fly-tips on Epping Forest land. Over the same period in 2019, there were 126.
Graeme Doshi-Smith, chairman of the Corporation’s Epping Forest Committee, said last year: "Fly-tipping is extremely bad for the environment and public health.
"It is also a waste of funds and time that could be better used to support Epping Forest."
Reports of fly-tipping should be made to the Corporation's 24-hour emergency line: 020 8532 1010.
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