Disgraced ex-lawmaker and union boss Brian McLaughlin is a secret witness in an FBI probe that led to Wednesday's arrest of a Queens pol on influence-peddling charges, the Daily News has learned.
The ongoing investigation - which featured an undercover FBI agent trolling the Assembly floor for corrupt pols - has snared its first collar: Assemblyman Anthony Seminerio (D-Ozone Park).
Sources familiar with the investigation said McLaughlin, a former assemblyman who pleaded guilty to bribery charges and faces up to 10 years in prison, is cooperating in the probe.
McLaughlin, once a major labor figure and a powerful force in Queens politics, faces sentencing later this week for stealing $2.2 million in cash, cars and perks.
Word that McLaughlin has flipped could send shivers across the city's political landscape.
As a seven-term legislator and ex-head of the million-member Central Labor Council, McLaughlin knows a lot about the dark corners of city politics.
His lawyer did not return calls seeking comment.
Seminerio is the only pol charged with a crime, although the federal complaint documents him schmoozing at least four other unidentified Assembly members and two unidentified state senators for his "clients."
Wednesday Assemblyman Robert Sweeney (D-Suffolk) confirmed he was one of those Seminerio lobbied. He has not been charged with wrongdoing.
Seminerio, who bragged in secretly taped conversations of his connections and clout, emerged glassy-eyed from Manhattan Federal Court after posting $500,000 bond.
The gruff 73-year-old ex-correction officer faces up to 20 years in prison. Asked for a comment as the couple trudged past reporters, his wife, Catherine, said, "Drop dead."
On tape, Seminerio was captured promising clients of his bogus "consulting firm" a full menu of insider's influence in return for payoffs.
"I am at your disposal. You tell me what you want. ... I'll take care of you," Seminerio told a hospital official in March. A month later, the assemblyman called another hospital executive to boast of his political access.
"That kind of relationship you can't buy for a million dollars," said Seminerio - who then reminded the official that he was owed a check.
Seminerio - whose battle with his waistline is as legendary as any of his political wars - launched Marc Consultants in 2000, authorities said.
A 17-page complaint says Seminerio's influence-peddling became so blatant that he twice brought the FBI agent into the Assembly. "Anthony Seminerio put his office up for sale for those willing to pay the right price," said Manhattan U.S. Attorney Michael Garcia.
The assemblyman was initially exposed by an informant who shared a 15-year friendship with Seminerio - and then introduced the politician to an undercover FBI agent last January. That informant was McLaughlin, sources said.
The agent made $25,000 in cash payments to Seminerio's business, the complaint charged.
Seminerio, in a taped September 2007 conversation with an informant, explained the launch of his phony firm, the idea for which he said he got from two unnamed senators.
"I was doing favors for these sons of bitches there. You know, they were, they were making thousands. Screw you, from now on, you know, I'm a consultant," said Seminerio, a 30-year assemblyman.
In one of Seminerio's schemes, federal prosecutors said, he collected $310,000 - a huge boost from his $79,500 state salary - from an unidentified hospital that received millions in state funding with his help.
With Kenneth Lovett, Glenn Blainand, Elizabeth Benjamin in Albany
