Campaigners have slammed the council after work began on tree clearance and woodland management around Astley Hall.
The Astley Park Coalition had asked for a stay of execution for the trees in front of the hall and adjacent to the duck pond.
But contractors were due to begin felling this week even though the issue of placing tree preservation orders (TPOs) on the area is in the hands of the local government ombudsman.
Cliff Jones, chair of the coalition, said: "For felling to begin on February 6 is nothing short of provocation especially since the matter is currently under investigation by the Ombudsman.
"I had to apply for TPOs to the council, the very authority which intends to cut the trees down. I see that as a direct conflict of interest.
"I have also been pressing for a comprehensive bat survey to be carried out as there is evidence that a variety of bat species roost in the trees.
"Under the Wildlife and Countryside Act 1981 it is an offence to interfere with the habitat of bats."
The woodland management work is part of a £1.8m heritage lottery funded restoration scheme for improvements to the park. A spokesman for Chorley Borough Council said: "Recent research into the landscape has shown that many of the trees around the hall are in the wrong place or have been planted in a haphazard way on the lawns.
"Trees are important components of this landscape however, and the mature beeches, limes and oaks will remain.
"This is the first phase of work which is essential if the next phases, which involve a new cafe and shop, a new pets corner and play area and restored walled garden, are to proceed."
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