A bestselling author writing about America’s most secretive intelligence agency is raising eyebrows with his claims that Israeli intelligence has potentially gained access to sensitive American communications information.

Investigative writer James Bamford contends in his new book, “The Shadow Factory, the Ultra-Secret NSA from 9/11 to the Eavesdropping on America,” that at least two high-tech companies with alleged ties to Israeli intelligence mined American communications data on a mass scale. The companies were hired to help major American telecommunications firms that were cooperating with the National Security Agency on its controversial eavesdropping program.

Bamford has written about the NSA, which conducts a wide array of electronic-surveillance activities, over the last quarter century. While some of the revelations in his latest book – NSA’s failure to act upon crucial information that could have prevented the 9/11 attacks and the abuses of the eavesdropping program – have received praise in the mainstream press, his Israel-related claims have been ignored by most and criticized by a few.

Michael Oren, an Israeli-American historian with the conservative Shalem Center in Jerusalem, charged that Bamford lacked proof to back up the Israeli-intelligence assertions made in the book. Oren has also criticized a previous Bamford book in which he accused the Israelis of purposely bombing an American spy ship off the Gaza Strip in 1967 during the Six-Day War.

“Bamford makes far-reaching and unsubstantiated allegations about Jews and Israel,” Oren told the Forward. “In the latest instance, he makes two serious assertions, namely that Israelis working in high-tech are Mossad and the Mossad works against the U. S. But in keeping with his previous work, there is no evidence.”

Bamford did not return inquiries seeking comment. And a spokesman for one of the companies named in the book said it did not engage in surveillance activities.

In a previous book, “Body of Secrets,” published in 2001, Bamford wrote that the bombing of the U.S.S. Liberty was intended to keep it from gathering data on what the author said was the Israeli massacre of hundreds of Egyptian prisoners of war. Israel consistently has said it had mistaken the American vessel for an Egyptian boat, an explanation accepted by the American government but contested by families of some crew members as well as several former American officials.

In his latest book, published in October by DoubleDay, Bamford writes that the largest American telecommunications companies cooperated with the NSA in the “warrantless eavesdropping program by allowing the agency to tap its phone lines and fiber-optic cables.” To do so, he writes, the telecom giants resorted to the assistance of at least two high-tech firms, Narus and Verint, founded in Israel and with alleged ties to its intelligence services.

Narus and Verint were involved in tapping phone and Internet communications for, respectively, AT&T and Verizon.

“AT&T have outsourced the bugging of their entire networks — carrying billions of American communications every day -— to two mysterious companies with very troubling ties to foreign connections,” he writes. “What is especially troubling, but little known, is that both companies have extensive ties to a foreign country, Israel, as well as links to that country’s intelligence service — a service with a long history of aggressive spying against the U.S.”

He then describes close ties between the Mossad’s Unit 8200, which he describes as the Israeli equivalent of the NSA, and several other Israeli high-tech companies doing business with the United States and other governments.

Bamford also stresses that the founder of Verint systems is wanted in the United States on multiple fraud charges and is a fugitive. The author refers to the Israeli-born Jacob “Kobi” Alexander, the founder of Comverse Technology, Verint’s parent company, who was indicted in 2006 on charges he backdated stock-options. Alexander is fighting American efforts to have him extradited from Namibia.

Both Verint and Narus were founded by Israelis and are now based in the United States. Verint did not respond to requests for comment. Narus lists AT&T as one of its customers on its Web site, along with clients in China, Egypt and Saudi Arabia.

Narus CEO Greg Oslan told the Forward through spokesperson Kathleen Shanahan that “the only ties Narus has with Israel is that the company was founded in the U.S. by a team that included Israelis. However, the original founders are no longer with the company.” She stressed that the company sells security, intercept and traffic management solutions to service providers and government organizations to help them protect and manage their complex Internet Protocol networks. “We do not engage in surveillance activities,” she said.

The Israeli embassy in Washington declined to comment.

Bamford, 62, served in a Navy unit that worked with the NSA during the Vietnam War. He then studied law before deciding to become an investigative writer. He also served as a producer for ABC News.

His first book on the NSA, published in 1982, was praised for shedding a rare light on an agency so shrouded in secrecy that its acronym is sometimes jokingly referred to as “No Such Agency.” His second book, published in 2001, hailed the agency for putting in place strong safeguards on its domestic spying activities. The latest one’s revelations that the NSA was listening in without proper warrants on the conversations of American soldiers, aid workers and reporters based in Iraq grabbed headlines in mid-October. But his claims about Israeli firms mining data on a mass scale on behalf of the NSA and his assertion that Washington’s support for Israel served as the main motivator for 9/11 have received little scrutiny in the mainstream media.

One exception is former Nebraska Senator Bob Kerrey, who in an otherwise favorable review published in the Washington Post, squarely disagreed with Bamford on Israel. “The author’s apparent negativity toward Israel is a significant distraction from the content of his book,” wrote Kerrey, the president of the New School in New York who was a member of the independent 9/11 commission. “And though I believe there has been too great a tendency to demonize the 9/11 terrorists by calling them cowards and worse, Bamford is entirely too sympathetic to them for my taste.”