New Jersey Senate President Stephen Sweeney on Wednesday accused the state's largest teacher union and the state Fraternal Order of Police of attempted bribery, saying each threatened to withhold campaign contributions if the Senate did not vote on a proposed pension-funding bill.

Sweeney (D., Gloucester) spoke at a news conference in Trenton and then released letters he sent to U.S. Attorney Paul Fishman and newly appointed state Attorney General Christopher Porrino that ask for a criminal probe into the New Jersey Education Association's actions.

Sweeney did not seek an investigation of the FOP. Sweeney "hopes and trusts" that the authorities "conduct thorough investigations of this matter, including looking at the involvement of any public labor union involved in making these threats," his representative said.

The NJEA has been one of the largest contributors to the state Democratic Party, providing millions through a super PAC to candidates. In the last year, however, NJEA members have staged protests against Sweeney, saying he reneged on a promise to schedule a vote that could lead to a ballot question in November on increasing state payments to the government workers' pension fund.

Wendell Steinhauer, president of the 200,000-member NJEA, said he was not concerned about Sweeney's allegations. He said his staff did nothing wrong when it recently contacted all of the state's Democratic senators and county party leaders to say the NJEA would not support their campaigns if the bill was not posted for a vote.

Steinhauer said the action did not constitute a bribe and was not a departure from past practice.

"We've been supporting the senators as long as they support our issues, and now we are deciding not to support them. Our support is not an entitlement; it is earned," he said.

Steinhauer said the staff phoned 24 Democratic senators and 22 party leaders, and some said they were disappointed about the rift. None of them, he said, told the staff they viewed the calls as a threat.

The union head said the accusations may stem from Sweeney's frustrations with the NJEA and the protests.

"We've been pushing on him, and this is his counterpunch," Steinhauer said.

The Senate would have to vote by Monday for the question to appear on the Nov. 8 ballot. The decision to schedule a vote lies with Sweeney alone. He has said he is focused on finding critical funding for transportation projects.

Sweeney said the teacher union's actions were "unprecedented tactics designed to extort public officials into undertaking actions that would benefit the pocketbooks of its members."

In the letters he wrote to authorities, he said, "These threats clearly cross the line from lobbying to attempted bribery and conspiracy. Essentially, the NJEA has put members of the N.J. state Senate in the position of tying specific official action to the receipt of a campaign contribution."

Luke Margolis, a Sweeney spokesman, said Sweeney wrote the letters on his own behalf because "as Senate president he has an obligation to display leadership and protect his members from this type of bullying."

At the news conference, Sweeney noted he also received a voicemail from Bob Fox, FOP president, saying the FOP would withhold contributions, too, if Sweeney did not call for the vote.

Fox did not return calls for comment.

In 2011, Sweeney and Gov. Christie, a Republican, hammered out a law that reduced health benefits for government workers and required the state to increase contributions to underfunded public pensions. Christie later reduced the contributions, which led to court battles, and then a proposal to put a constitutional amendment on the ballot increasing payments.

Steinhauer said Sweeney promised the union in February that he would post the pension bill for a vote this summer.

"But now he is holding up the bill because he is tying it to the Transportation Trust Fund issue," Steinhauer said. "But this bill has nothing to do with the Transportation Trust Fund."

jhefler@phillynews.com 856-779-3224 @JanHefler