A national parks advocacy group wants Congress to fund the purchase of sites in Virginia.

Hundreds of acres of land inside many national parks — including some Civil War sites in Virginia — are at risk because they remain in private hands, according to a new report by a park advocacy group.

The land remains private, the group says, because money that was supposed to be used to buy the land has been diverted away from the National Park Service altogether. The park service's appropriation of money for land purchases has declined from $148 million in 1999 to $44 million in 2008.

In fact, the National Parks Conservation Association said, $14.7 billion of the $29 billion in oil and gas royalties that was supposed to go to the Land and Water Conservation Fund since 1965 has been diverted for other purposes.

Many parks are dotted with privately owned land, called inholdings, inside their borders. Most often the land was there when the park was created and the National Park Service keeps a running priority list of which properties to buy when the seller is willing and money is available.

That money is becoming less and less available as Congress continues to divert it, the NPCA said. "This is about protecting the integrity and completing the mission of the National Park Service," said Ron Tipton, a senior vice president at the NPCA.

Tipton said government officials have ordered the purchase of these properties then failed to provide the money. The NPCA is asking Congress to boost funding by $100 million this year to buy the highest priority lands.

In Virginia, the report identifies privately held land at four Civil War sites: 230 acres near Fredericksburg where the Battle of the Wilderness was fought in May 1864; five acres at Appomattox Courthouse; 10 acres at Manassas; and 356 acres inside the boundaries of Richmond National Battlefield Park.

On the outdoor recreation and wilderness side, the report identifies 765 acres at two sites along the Appalachian Trail; 1,900 acres at Cumberland Gap National Historical Park (which stretches into Tennessee and Kentucky); and 180 acres at Prince William Forest Park, a popular camping spot in Northern Virginia.

Just across the border in West Virginia, the report called special attention to 66 acres at Harper's Ferry — where John Brown stormed a U.S. arsenal in an attempt to arm a slave uprising in 1859 — that are particularly threatened by encroaching development. The land could be bought for $7 million, the report said.

Jeffrey Olson, a spokesman for the National Park Service, said the Bush administration and park superintendents have focused on operations over land holdings.

"In the current administration, with a lot of input from the parks, the emphasis is on operations, not expanding the system," he said. "We have been hammered by the cost of operations."

Olson said the park service is always evaluating its list of potential inholdings to buy. "It's a long list," he said. "It is a matter of money being available." It's also a matter, he said, of, "what is the cost of adding to the system? Is the financial will going to accompany the political will? Those are the only things we point out."