"There is no sign the government is moving in the right direction," said Dimitris Karavellas, warning that some of the land was so badly damaged it could not regenerate itself.
But Prime Minister Costas Karamanlis thanked pilots who fought the fires and said they had "surpassed the limits of human endurance".
"Close your ears to those few who, from a safe position for their own expediencies attempt to criticise everything," he said.
As winds eased, a Greek fire brigade spokesman, Yiannis Kappakis, said emergency services were close to taming the blazes, saying there were "no significant active fronts".
But he warned that there was still some risk.
"The danger of the fires flaring up again is not yet over," he said.
Waterbombing planes were sent to tackle fires still burning on Mount Kithaironas, west of Athens, and in Karystos, on the island of Evia.
Officials said the blazes did not, however, pose a threat to inhabited areas there.
Conspiracy theory
Since Saturday, thousands of residents of the capital's northern suburbs have been forced to abandon their homes.
Nearly 2,000 firefighters, including a Cypriot contingent, and soldiers have been engaging the blaze on the ground, together with hundreds of volunteers.
Two additional waterbombing planes from Spain were expected to arrive on Tuesday.
There have been allegations that the wildfires were started as part of a well-organised conspiracy to clear the area for property development.
The fires began late on Friday in Grammatiko, near Marathon. They are the worst since those in 2007 which killed about 70 people.
In July, dozens of fires burnt through thousands of hectares of land in other parts of Greece, Spain, France and Italy.
According to the conservation group Greenpeace, heat waves and drier conditions are leading to larger and more uncontrollable forest fires across the whole Mediterranean region.
Video map: How fires in Greece have spread
Fires flare overnight in Greece
Greek firefighters battle wildfires that threaten areas north of Athens, as thousands leave their homes.
Amateur video of smoke 'blanket'
Raging wildfires threatening Athens have been described as the region's worst-ever environmental disaster.
'Smoke was blocking out the sun'
Major wildfires north-east of the Greek capital Athens are burning out of control, officials have said.
Fleeing from raging Athens fires
The BBC's Malcolm Brabant tells his first-hand account of escaping wildfires in the Athens suburbs.
Greek fires rage into the night
Wildfires outside Athens rage into the night - the worst blazes on the mainland since 2007, officials say.
Click video icons to see reports from affected communities near Athens. The fires began to the north-east, near Grammatiko, on Friday, before being driven closer to the capital by strong winds.
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