ANCHORAGE — U.S. Attorney General Loretta Lynch has denied a request by the prosecutors for the state of Alaska who want to use federal laws to charge a businessman who testified in the corruption trial of the late Sen. Ted Stevens.

In a letter Tuesday to Alaska Attorney General Craig Richards, Lynch said a prosecution of Bill Allen on federal child exploitation charges would be improper.

The case does not meet standards for the principles of federal prosecution, she said. Such charges can be brought only when “the admissible evidence probably will be sufficient to obtain and sustain a conviction,” Lynch said.

The decision was not connected to any sort of a deal for Allen’s testimony in corruption cases, Lynch said.

Allen, the wealthy head of a high-profile Alaska-based oil field service company and former publisher of the now-defunct Anchorage Times newspaper, has denied allegations of misconduct.

He was at the center of a federal investigation of corruption in Alaska politics. He pleaded guilty to bribery and testified in the trials of three Alaska elected officials, including Stevens, his one-time friend.

Stevens was charged with failing to report gifts, including major renovations by Allen’s company to Stevens’ home in Girdwood. A jury verdict against Stevens was set aside and the indictment dismissed amid charges of prosecutorial conduct. By then, Stevens had lost his re-election bid. He died in a plane crash in 2010.

Richards in February said federal and Alaska investigators found evidence that Allen violated the federal Mann Act by transporting an underage prostitute across state lines from Seattle to Anchorage for sexual purposes.

The state twice asked the federal Justice Department to allow state lawyers to prosecute Allen under the federal law and twice was denied, without reasons, Richards said.

U.S. Sen. Dan Sullivan, R-Alaska, pushed the issue last year with a change to the federal Mann Act. His amendment requires the U.S. attorney general to grant state requests for “cross-prosecution” under federal law unless granting that request would “undermine the administration of justice.” If the request is denied, a detailed reason must be provided within 60 days.

Alaska’s third request for cross-prosecution was made in February.

Sullivan in a statement Tuesday said he found it frustrating that it took the threat of violating a new federal law to get a direct answer regarding the prosecution of Allen.