Alleging unfair business practices they say could prove ruinous for New England's largest convention, exhibition, and hotel complex, Bayside Expo owners are going public with complaints that the still-in-construction Boston Convention and Exposition Center (BCEC) is stealing clients.

While BCEC officials deny the charges, Bayside's owners, the Corcoran Jennison Company, are hoping for assistance from elected officials, and last week gave tours of the facility to several Dorchester and South Boston politicians.

The politicians have lined up behind Bayside, but Jim Rooney, acting director of the Massachusetts Convention Authority, which runs the BCEC, said any legislative means of resolving the dispute will prove fruitless. Rooney said he would sign an agreement that mediates the conflict, but not one he deems "overly restrictive."

Joseph J. Corcoran, head of development at Corcoran Jennison's expo divison, said in an interview last week that the decision by the Boston Gift Show earlier this year to end its two-decade relationship with Bayside and sign a three-year contract, effective 2005, to stage its event at the BCEC is indicative of a creeping rivalry that "very negatively impacts our business." Corcoran said the gift show accounts for eight to 10 percent of Bayside's business, a figure Rooney questioned.

George Little Management, the company that runs the Boston Gift Show, delivered to Corcoran this spring its decision to switch venues, claiming it had outgrown the Bayside space. Corcoran has since hosted tours for state Senator Jack Hart, state Representatives Martin Walsh and Brian Wallace, and City Councillors Maureen Feeney and Michael Flaherty, all of whom attested that Bayside appeared to offer ample space. Walsh said the building, nudging the South Boston border, appeared "probably a third empty."

Lynn White, the George Little group show manager in charge of the show, disputed that, and said company's September show is generally smaller than its March show.

White said that space was one factor in the company's decision, adding that location and a different floor plan also weighed in. The BCEC's South Boston location provides easier access to downtown restaurants.

Bayside, located on Columbia Point and adjacent to the Corcoran Jennison office building that houses the Reporter offices, would suffer a big hit if more "gate shows" head for the Convention Center. Corcoran said he fears the lone incident could become a trend.

Corcoran and Rooney agree that the two venues don't compete for conventions that draw nationally; Corcoran insists his building pulls from the regional population, and is designed for such: 2,000 parking spaces, with easy access to the highway. It is ideal, he said, for gift shows, where attendees from various industries are invited to purchase goods.

"The key thing there is that the guy is driving in that day, and he's driving home that night," Corcoran said. "He's not staying in a hotel, and he's eating dinner with his family. The convention center wasn't built for that."

Rooney argues back that the competition over the Boston Gift Show is "on the margins," the result of "incidental overlaps."

"If the Bayside and the World Trade Center and some other venues can allow shows to be successful and grow up to the big hall, that's a good thing," Rooney said.

But he called attempts to impose legal strictures on BCEC clients unfair, and "maybe unconstitutional."

"You can't have someone who walks into Shaws' get told they've got to go shopping at Stop & Shop. And that's what [Corcoran] wants us to do."

"I think the Bayside and the World Trade Center could be good incubators," Rooney said.

Wallace, of South Boston, said the competition is unfair, and agreed with Corcoran and his colleagues that a written compromise should be reached that restricts the BCEC from drawing business from Bayside and the World Trade Center.

"The convention center was built because they were trying to attract a certain type of business, not steal other people's business," Wallace said. "There has to be a certain niche here for everyone, so it's not a lose-lose proposition."

Hart has arranged a meeting this month between Corcoran and Rooney to attempt to mediate a settlement.

In the meantime, after it jumps ship in two years, Bayside visitors are not likely to see the Boston Gift Show again. White said George Little is "not considering" moving back to Bayside.