Updated: 9:45 a.m.

The Minnesota-based company 3M sued lawyer, lobbyist and public relations guru Lanny Davis last week, accusing him of orchestrating a “smear campaign” on behalf of a client trying to settle a breach-of-contract claim.

Davis said the allegation of a “smear” campaign is “harmful and false,” and that he was simply engaging in routine public relations activities.

The case, which was filed Aug. 24 in the U.S. District Court for the District of Columbia, names Davis; his affiliated enterprises; his client, Porton Capital; and Porton’s chief executive as defendants in a lawsuit that describes a “conspiracy” to “unlawfully coerce one of the world’s largest and most successful companies, 3M, into paying tens of millions of dollars” by disseminating false information to the media.

“Davis’s offices in Washington, D.C., served as the ‘nerve center’ of a campaign to coerce and intimidate 3M into paying Defendants tens of millions of dollars under the guise of ‘settling’ a lawsuit that was then pending in the U.K.,” the complaint stated. It accused Davis of leading “a smear campaign that began as a defamatory media blitz and culminated in the outright attempted blackmail of 3M.”

Davis dismissed the lawsuit Wednesday as a tactic meant to divert attention from the original breach-of-contract case, which is drawing to a close in England. He described the lawsuit as 3M’s latest attempt to “harass” his client after 3M tried to bring a nearly identical case before a New York state court, then unsuccessfully sought to have it transferred.

“3M and its attorneys have now filed the same suit for the third time,” Davis said in a statement. “But no matter how many times they file meritless lawsuits against my client and me as its attorney, they can’t change the subject or the facts about their unwillingness to fulfill their contractual commitments.”

Attorneys for 3M said late Wednesday that they had filed the suit in Washington because the New York case had become delayed by Davis and other defendants.

The dispute between the two companies began when 3M acquired a company named Acolyte, which had developed a device to screen hospital patients for “super bugs” that resist antibiotic treatment. As a selling shareholder of Acolyte, Porton Capital was entitled to payments based on net sales of the device through the end of 2009.

But when 3M conducted clinical trials to obtain approval from the Food and Drug Administration to sell the product in the United States, results showed that the test was far less accurate than initially believed, the lawsuit said. 3M decided to stop marketing the product and offered to pay invested parties a sum based on projected sales, but Porton Capital rejected the offer and filed the breach-of-contract case in the United Kingdom.

That case went to trial in June, and closing arguments are scheduled for late September.

Davis said the timing of the stateside lawsuits was a diversionary tactic to gain leverage in the overseas litigation.

“It’s changing the subject from what’s going on in London,” he said.