"Some of the experts working for us were [also] visited by secret service agents, asking about their international relations with foreign organisations or movements," one unnamed person told EurActiv.
A leader of the green NGO Eko-Unia also said that his friends have received visits from secret police officials asking about his environmental activities.
The environmental groups singled out one recent quote in particular by the Minister of Treasury, Mikołaj Budzanowsk, as evidence of pressure against the country's NGOs.
In an interview with the Polish media this month, Budzanowsk said, "This kind of organisation should accept that there are limits to its activities. In my opinion they have passed their limit. If I were ClientEarth (…) I would reconsider doing any further work against [the Polish Energy Group]."
Since 2010 about 25 exploration wells have been drilled in the country’s shale.
Polish activists have disrupted meetings of energy corporations over the past year, including with a flash mob and "Frack You" banner last November at a meeting between Halliburton, Talisman Energy, Dow Chemical and the Polish government.
Still, government ministers say the environmental groups may not be representing the best interests of Poles.
"It is rather unclear whether such [environmental] organisations represent the interests of local communities or rather some unidentified interests, which are not always very clear or pure of intention," Michał Gołębiowski, the deputy director the Polish treasury ministry's department of strategic projects, told EurActiv.