Haringey Friends of Parks Forum said it would fight the 50 per cent budget cut to £1.2m in April. The group said this had led to neglected flower beds and "mountains of litter" in several parks.
Forty-six of the borough's main parks, including Finsbury Park and around 40 smaller community spaces, are looked after by the council. But cuts had led to the axing of upkeep for some parks and a worsening in quality, said forum member Dave Morris.
Morris, also vice-chair of the National Federation of Parks & Green Spaces, said the petition to reverse cuts notched up more than the 2,200 votes needed to trigger a debate at the council.
However, the council did not vote on the debate and also threw out an emergency motion on reversing the cuts by two independent councillors on a technicality, said Morris, who recently helped organise an anti-cut demo.
"The parks department is in crisis," he said. "We will keep lobbying to ensure our green spaces are managed to the standard a community should expect."
Forum secretary Joan Curtis said council officers had been asked to run parks "on the cheap", pinning hopes on volunteering, probation and work-for-dole schemes.
But Councillor Alan Strickland responded: "We won't return to the dark days of the 1970s, 1980s and 1990s. Resources are tight but no park will go unmaintained or be abandoned."
Parks consultant David Lambert said: "The size of the cut is astronomical and the impact incalculable. This is happening all around the country and all the Green Flag and lottery investment is being undone."