The Forestry Commission says grant aid is available for broadleaf planting
The Forestry Commission is not following policies to protect Wales' indigenous woodlands closely enough, according to a tree charity.
Coed Cadw - the Woodland Trust in Wales - says clear-felling, cutting down all the trees in an area, is harmful to habitats and wildlife.
The Forestry Commission said it was increasing broadleaf tree planting and clear-felling could help as a catalyst.
The assembly government is expected to make a woodland announcement in 2009.
The Labour-Plaid coalition agreement promised to support indigenous woods and create a Welsh national forest.
Rory Francis, from Coed Cadw, said that clear-felling was harming Wentwood Forest near Newport, one of Wales' largest ancient woodlands.
"The problem is that the old policies are still being followed and there are parts of Wentwood where you can see clear-felling has happened, you can see damaging ground preparation.
"We understand whole new crops of conifers will be planted and that's caused more problems already - it looks ugly, it's unpopular, but that new crop of conifers will destroy even more of those ancient woodland relics that make the place special."
Around 900 acres of Wentwood Forest is owned and managed by Coed Cadw.
It also harvests trees commercially, but it believes clear-felling for possible replacement with more conifers goes against the assembly government's aims.
The One Wales coalition document agrees to provide support for indigenous woodlands and help to create a "Welsh national forest of native trees to act as a carbon sink."
Neil Stoddart, a forest district manager for the Forestry Commission at Llandovery in Carmarthenshire, said although conifer production was an important part of rural economic development, it could be balanced with environmental gains.
"There are clear fell operations still going on across the estate - they are fewer on ancient woodland sites, however we have to ensure that we meet our stakeholders' objectives and some of the greater, wider biodiversity gains are achieved through clear-felling.
"Clear-felling on ancient woodland sites allows the forest manager to ensure that whilst we don't damage any remnants, we are able to act as a catalyst and ensure we put some broadleaf woodland back in a shorter timescale.
"In the private sector we are able to offer enhanced grant aid for broadleaf planting and in the public sector we certainly have the drivers there to ensure we increase the broadleaf plantings across the whole estate."
Rural Affairs Minister Elin Jones is expected to make an announcement of woodland in the new year.