Democratic presidential frontrunner, Senator John F Kerry, sent 28 letters between 1996 and 1999 on behalf of a San Diego defence contractor who pleaded guilty last week to illegally funnelling campaign contributions to him and four other congressmen, according to the Los Angeles Times.
Kerry wanted federal funds for a guided missile system that contractor Parthasarathi 'Bob' Majumder was trying to build for US warplanes.
Majumder's firm, Science and Applied Technology Inc, was paid more than $150 million to design and develop the programme, which ran into trouble at the Pentagon.
Kerry's letters were sent to fellow members of Congress and to the Pentagon, while Majumder and his employees were donating money to the senator, the paper said, citing court records.
Kerry received about $25,000 from Majumder and his employees during the three-year period, according to Dwight L Morris & Associates, which tracks campaign donations.
Last week Majumder, 52, pleaded guilty to two counts of illegal campaign contributions. He could be sentenced to six years in prison. The government dropped 38 other counts, the paper added.
The plea followed a December 18 civil settlement in which Majumder agreed to pay the government about $3 million for submitting false claims under a government contract. He acknowledged making more than $95,000 in illegal donations to Kerry, Rep Duncan Hunter, Rep Randy 'Duke' Cunningham, Rep John Murtha and Rep Joe Scarborough, who is now retired.