Dow Chemical manufacturer Sasol North America and its contractors hired private investigators to spy on the environmental group Greenpeace, according to a new lawsuit.

The 56-page lawsuit, filed by Greenpeace Monday in federal district court in Washington, says the companies and public relations firms Dezenhall Resources and Ketchum hired investigators who stole documents, tapped phones and hacked into computer networks between 1998 and 2o00.

"We believe it is every citizen's right to stand up for the health of their children and community without fearing retribution, an invasion of privacy, conspiracy against them or theft of their belongings," said Phil Radford, executive director of Greenpeace USA.

At the time, his group was campaigning against toxic pollutants such as dioxin that it said the companies were releasing, specifically in the Lake Charles, La., area. An April 2008 article by James Ridgeway in the magazine Mother Jones first reported the alleged corporate spying effort.

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Spokespeople for Dow, Sasol and Ketchum, a part of the Omnicom Group, and Eric Dezenhall, chief executive of his District-based firm, declined to comment on the complaint's specifics, reportsThe Washington Post.

"We have not been served with this suit and, therefore, we are not in a position to immediately comment about the alleged activities of over a decade ago," Dow spokesman Bob Plishka said in a statement.