PROVIDENCE — A former organizer for the Laborers’ International Union of North America and a longtime contractor were charged yesterday with conspiracy to commit labor racketeering for allegedly making and receiving kickback payments on a development in the Olneyville section of Providence.

An affidavit in support of the criminal charges against Harold Tillinghast, 44, of Cranston, and Gerald Diodati, 59, of Seekonk, harkens back to the days of smoky backroom deals when labor officials, contractors and mobsters worked in concert to line their own pockets.

The criminal investigation, which was launched six years ago, is being prosecuted by two veteran assistant U.S. Attorneys assigned to the Justice Department’s Organized Crime and Racketeering Section in Washington, D.C.

A key figure in the probe is Matthew L. Guglielmetti Jr., a capo regime in the Patriarca crime family, who is serving a lengthy federal prison sentence in Fort Dix, N.J. At one point, according to the affidavit, Guglielmetti told an undercover FBI agent that “his status as a member of La Cosa Nostra afforded him special influence with the Laborers International Union of North America in Rhode Island and elsewhere.”

The investigation began in 2002 when the FBI opened a fictitious construction firm, Hemphill Construction, which was seeking work in Rhode Island and elsewhere in Southern New England. The business was in a retail plaza on Atwood Avenue, just off Route 6, in Johnston.

A few months after setting up shop, an undercover FBI agent, posing as a Hemphill Construction principal, met with Diodati and Tillinghast. They allegedly reached an agreement that Diodati and unnamed others would make cash payments to Tillinghast in his role as a Laborers’ Union official.

The undercover FBI agent signed a collective-bargaining agreement on behalf of Hemphill with the Rhode Island Laborers District Council which included the Laborers’ union Local 271, in Providence.

In April 2003, Tillinghast allegedly told Diodati and the undercover FBI agent that he would try to get Hemphill Construction a demolition contract with Rising Sun Mills, a redevelopment project on Valley Street in Olneyville.

Diodati prepared a bid for $977,000 on behalf of Hemphill Construction for demolition work on the project.

A few weeks later, Diodati and the undercover agent met at Hemphill Construction’s offices and discussed making a $2,000 kickback to Tillinghast to help sway him to give Hemphill the demolition project.

The payment was allegedly made and Hemphill was awarded the contract.

Around that same time, Diodati formed a new corporation, Rhode Island Demolition, to perform the work as a subcontractor for Hemphill Construction.

A few months later, on Oct. 7, 2003, the undercover FBI agent met with Tillinghast at a Starbucks Coffee shop in Cranston. There, the agent told the union official that mobster Guglielmetti was a silent partner in Hemphill Construction.

Tillinghast, according to the affidavit, responded that “because of Guglielmetti’s involvement, he now had to work harder on behalf of Hemphill Construction to get it more contracts.”

On Oct. 23, the undercover FBI agent met with Tillinghast and Guglielmetti in Johnston. Tillinghast allegedly said that he was “upset” because Diodati and his firm, Rhode Island Demolition, were using nonunion labor for Hemphill Construction at Rising Mills. Tillinghast said that he had to “come down” on Diodati, the affidavit says.

Over the next two months, Diodati attempted to iron out his differences with Tillinghast and the labor union. At one meeting, he told the undercover agent and Guglielmetti that Hemphill Construction should provide a “package” to a Laborers’ union official and that the firm should cover the payment of a $500 car rental to the same official.

A few weeks later, Diodati told the undercover FBI agent that he would “give liquor and gift certificates” to a local restaurant as Christmas gifts to several Laborers’ union officials. Tillinghast later confirmed to the FBI undercover agent that the gifts were dropped off at the union’s headquarters on South Main Street in Providence.

In 2005, Diodati, who spoke to two Journal reporters in his house, said that he was unaware he was assisting undercover FBI agents. He said that he agreed to meet with the Hemphill partners as a favor to a friend, whom he declined to name.

In February 2007, the Journal reported that Diodati hired Tillinghast’s uncle, Gerald M. “Gerry” Tillinghast, a mob hit man, to work for his firm that was transforming a former textile mill in Coventry into luxury apartments.

Tillinghast was hired five days after he was released from the Adult Correctional Institutions after serving nearly 30 years in prison for the gangland slaying of George Basmajian.

In U.S. District Court yesterday, Tillinghast and Diodati were released on $25,000 unsecured bond and their travel was limited to Rhode Island and/or Southeastern Massachusetts. Diodati asked Judge Lincoln D. Almond whether he could go to Boston and Connecticut to seek government contracts for his construction firm.

“There is no work in Rhode Island,” he said. “Rhode Island is like the desert when it comes to government work.” Almond granted the request.

bmalinow@projo.com